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Extinct proboscideans - Mammoths, mastodons and other elephant relatives from the Pleistocene epoch of the Midwest Proboscidea Midwestern Elephant Relatives During the Pleistocene Epoch, the Midwest was home to several large proboscideans, the group of mammals that includes modern elephants. These animals represented many different forms of elephant-like mammals, including mammoths, mastodons and gomphotheres. Mastodons preferred forested environments, where they browsed on leaves, twigs, and shrubs, while mammoths were more adapted to open grasslands and fed primarily on grasses. Gomphotheres formed a group with a convoluted taxonomic history, possibly even including the direct ancestors of mammoths and living elephantids, as well as a diverse array of strange four-tusked extinct proboscideans. In the Pleistocene epoch, the last members of the gomphothere group were animals like the spiral-tusked Cuvieronius . Fossil discoveries across Midwestern states such as Kansas, Missouri, Iowa, Illinois, and Indiana show that these giant mammals were important members of Pleistocene ecosystems until their extinction near the end of the Ice Age. Anatomy (BELOW) Features of the skulls of proboscideans, in this case the gomphothere Cuvieronius. The large tusks found in many types of proboscideans are composed of a pair of enlarged incisors. Some proboscideans had lower jaw tusks as well. Skull and Dentition One of the defining features of proboscideans both living and extinct is their large, highly modified skulls. In many proboscideans, the skull is saturated with air-filled cavities that make the bones more lightweight without losing the strength needed to hold the mass of the trunk and tusks. Living elephants have a tall, sometimes domed skull with enlarged nasal openings situated high on the face. This position is linked to the shape of the base of the trunk. Extinct proboscidean groups each had their own special suites of skull features which ranged from the longer, lower-profile skulls of amebelodontids which often held long tusks on their lower jaws, as well as the more familiar skull shapes seen in animals like mammoths. The teeth of proboscideans changed quite a bit over the course of their evolutionary history as well. Early members of the group had a larger number of teeth than their modern relatives and had relatively simple molars with low crowns. Over time molar structure became increasingly specialized. Mastodons had molars with tall cusps suited for browsing on woody vegetation, while mammoths and modern elephants evolved large flattened grinding teeth characterized by multiple enamel ridges which are perfect for chewing up grasses and other tough silicate-rich plant matter. In many species the upper incisors eventually turned into tusks which, depending on the genus, could be straight, curved or even spiral-shaped. (BELOW) Lower jaws of two types of extinct proboscideans on display at the KU Natural History Museum. Mammoth jaw on the left side of the image, mastodon lower jaw on the right. Note the differences in the shapes of the molars. Postcranial Skeletal Anatomy Most proboscideans were/are rather large animals. As a result of their size, most of their skeletal anatomy is adapted for holding up extreme amounts of weight. These animals have massive, pillar-like limbs which are thick and heavily reinforced. Their nearly vertical orientation beneath the body helps to reduce mechanical stress as these animals move. Compared with many other mammals, the lower limb joints of proboscideans are quite inflexible and are supported by a cushioned pad beneath each foot. Their vertebral columns and rib cages are similarly sturdy and often very wide. (BELOW) A labeled diagram of the skeletal anatomy of a Columbian mammoth, based on the skeletal mount from the University of Nebraska State Museum of Natural History. External Anatomy Modern elephants have relatively little body hair and, in many species, they additionally have large ears that they can use to cool down by flushing them with blood. In contrast, woolly mammoths and possibly some mastodons were covered by a thick coat of fur and an insulating underlayer, adaptations for survival in cold environments. Proboscideans living in colder climates also likely had smaller ears in order to keep their body heat from escaping. Mammoths and other Pleistocene proboscideans living in warmer climates may have had mostly hairless skin like that seen in living elephants. (BELOW) Features of the external anatomy of the proboscidean Stegomastodon from the early Pleistocene epoch Cuvieronius hyodon Temporal Range: 10 million years ago to approximately 10,700 years ago Geographic Range: Found across North and South America Species: C. hyodon, C. tropicus, C. oligobunis, C. priestleyi Diet: Herbivorous mixed feeder, grass, leaves Cuvieronius was an elephant-like proboscidean belonging to the trilophodont gomphothere group. It was one of the last surviving gomphotheres and ranged from the southern regions of North America through Central America before eventually spreading into South America. Unlike mammoths and mastodons, Cuvieronius had distinctive tusks that twisted in a gentle spiral. Its lower tusks were greatly reduced or absent in adults. Fossil evidence indicates that it would have lived in a variety of environments, including open grasslands, woodlands, and subtropical habitats. Its flexible diet allowed it to consume a wide range of vegetation rather than specializing on either grasses or browse. A few sites seem to show the remains of Cuvieronius preserved alongside stone tools, suggesting that the first humans to arrive in the Americas hunted these gomphotheres. Columbian mammoth Mammuthus columbi Temporal Range: 1.5 million years ago to approximately 12,000 years ago Geographic Range: Genus across North America, Central America Species: M. columbi Diet: Herbivorous grazer, grasses The Columbian mammoth was the largest land mammal found in the Midwest during the Pleistocene. Up until around 12,000 years ago mammoths would have been a common sight all throughout North America. Their range extended from North Dakota all the way down to central Mexico and their remains are found along both the Atlantic and Pacific coasts. Mammoths were at home in grassland habitats where they would have lived alongside giant bison, camels and wild horses. The average adult Columbian mammoth would have stood around 12 feet tall at the shoulder, although some very large individuals may have reached heights of 14 feet making them much larger than any elephant species alive today. A particularly large example of a Columbian mammoth skeleton, nicknamed Archie, is on display at the Nebraska State Natural History Museum in Lincoln. This particular specimen is one of the largest mounted mammoth skeletons in the world. (ABOVE) A skeleton of a Columbian mammoth, nicknamed "Archie" on display the University of Nebraska State Museum of Natural History, Morrill Hall. Woolly mammoth skeleton in the background on the right. (ABOVE) An adult mammoth tooth (left) compared with a tooth from a juvenile (right). Mammoths and other proboscideans lost their teeth as they got older and new sets moved in to take their place. Teeth are on display at the KU Natural History Museum in Lawrence, KS. Woolly mammoth Mammuthus primigenius Temporal Range: 400,000 years ago to approximately 4,000 years ago Geographic Range: northers latitudes of North America, Eurasia Species: M. primigenius Diet: Herbivorous grazer, grasses Woolly mammoths were fairly rare in the Midwest. They were almost entirely absent in the southern parts of the Plains and even in parts of South Dakota they seem to have been outnumbered by their larger relatives, the Columbian mammoths. At the Mammoth Site in Hot Springs, South Dakota, a Pleistocene bone bed preserves the remains of dozens of Columbian mammoths but only three woolly mammoths. Woolly mammoths are well known for their thick coats of fur which would have offered them a great deal of protection from the cold. Some mammoth mummies have even been found with some of their fur coats still intact. Mammoths had longer legs than most of today's elephants and had a distinctive dome on top of their foreheads. The last of the woolly mammoths disappeared from a small island in the Arctic called Wrangel Island around 4,000 years ago, although by then they had been extinct on the mainland for thousands of years. American mastodon Mammut americanum Temporal Range: 8 million years ago to approximately 11,000 years ago Geographic Range: Genus is found across North America Species: M. americanum, M. pacificum, M. nevadanum Diet: Herbivorous browser, leaves American mastodons were some of the first large animals whose fossils were recorded as having been found in North America. Their bones were likely found across the continent for thousands of years but the first recorded find of one of their fossils is likely a piece of a tooth surface found sometime around 1705. Early in their history of study, in the 19th century, the large cusps on the teeth of these animals were interpreted as a sign that they were carnivorous, although this idea was soon dismissed. We now know that these large cusped teeth were likely an adaptation for feeding on woody plant material. Mastodons were found all across North America, from Alaska to central Mexico. These animals could be differentiated from mammoths by their stockier builds, straighter tusks, unique tooth surface shapes, and the lack of a large bony dome over their foreheads. They preferred to live in forest habitats. Although these animals are typically reconstructed with a thick coat of fur, some researchers have suggested that they might not have been very hairy after all, with their stockier build keeping them warm even in colder areas. This is still an unresolved question and future finds may give us more information about the life appearance of these ancient animals. The American mastodon also has an important cultural presence in the US and has been designated the official fossil of the states of Michigan and Indiana! (ABOVE) A mastodon tooth on display at the KU Natural History Museum. The tall cusps on these teeth were well adapted for processing woody browse. Worn teeth of this size are found in older individuals. (ABOVE) A mastodon skeleton on display the University of Nebraska State Museum of Natural History, Morrill Hall. Unlike mammoths, these mastodons did not have a prominent dome on their foreheads. Stegomastodon nebrascensis Temporal Range: 4 million years ago to 1.2 million years ago Geographic Range: Found throughout North America Species: S. nebrascensis, S. mirificus, S. aftonae, S. primitivus Diet: Herbivorous mixed diet, grasses, leaves Stegomastodon was an extinct proboscidean belonging to a group called the trilophodont gomphotheres. These were extinct elephant relatives that had flourished in North America during the Neogene period but became increasingly rare during the Pleistocene. Stegomastodon lived in North America from the Pliocene into the early Pleistocene. Unlike earlier gomphotheres, which often had elongated jaws with a second set of lower symphysial tusks, Stegomastodon had a short lower jaw and only a pair of upper tusks, giving it a more elephant-like appearance than some of its ancestors. Its tusks curved upward and could reach impressive lengths. Fossils of Stegomastodon have been discovered across much of North America, indicating that it occupied a wide range of habitats. These animals were once thought to have lived in South America but those southern species have since been folded into the genus Notiomastodon . (ABOVE) A skeleton of Stegomastodon on display the University of Nebraska State Museum of Natural History, Morrill Hall. Note the length of the tusks in this animal and the width of the bones of the ribcage and pelvis Media Gallery Suggested References: Proboscidea Bader, Camille; Delapré, Arnaud; Göhlich, Ursula B.; Houssaye, Alexandra (2024). "Diversity of limb long bone morphology among proboscideans: how to be the biggest one in the family". Papers in Palaeontology. 10 (6) e1597. Dooley Jr., Alton C.; Scott, Eric; Green, Jeremy; Springer, Kathleen B.; Dooley, Brett S.; Smith, Gregory James (2019). "Mammut pacificus sp. nov., a newly recognized species of mastodon from the Pleistocene of western North America". PeerJ. 7 e6614 Louguet-Lefebvre, Sophie (2013). "The Columbian mammoths from the Upper Pleistocene of Hot Springs (South Dakota, United States)". Paléo. 24 (24): 149–171. Pérez-crespo, V. A.; Prado, J. L.; Alberdi, M. T.; Arroyo-cabrales, J.; Johnson, E. (2016). "Diet and habitat for six American Pleistocene proboscidean species using carbon and oxygen stable isotopes". Ameghiniana. 53 (1): 39–51. Lucas, Spencer G.; Aguilar, Ricardo H.; Speilmann, Justin A. (2011). "Stegomastodon (Mammalia, Proboscidea) from the Pliocene of Jalisco, Mexico and the species-level taxonomy of Stegomastodon". New Mexico Museum of Natural History and Science Bulletin. 53: 517–553. Mothé, Dimila; Avilla, Leonardo S.; Cozzuol, Mário; Winck, Gisele R. (2012). "Taxonomic revision of the Quaternary gomphotheres (Mammalia: Proboscidea: Gomphotheriidae) from the South American lowlands". Quaternary International. 276–277: 2–7. Mead, Jim I.; Arroyo-Cabrales, Joaquin; Swift, Sandra L. (2019). "Late Pleistocene Mammuthus and Cuvieronius (proboscidea) from Térapa, Sonora, Mexico". Quaternary Science Reviews. 223 105949. Mothé, Dimila; Avilla, Leonardo S.; Cozzuol, Mario A. (2012). "The South American Gomphotheres (Mammalia, Proboscidea, Gomphotheriidae): Taxonomy, Phylogeny, and Biogeography". Journal of Mammalian Evolution. 20: 23–32. Nabavizadeh, Ali (2024). "Of tusks and trunks: A review of craniofacial evolutionary anatomy in elephants and extinct Proboscidea". The Anatomical Record. 308 (11) ar.25578. Sanders, William J. (2023). "Chapter 3:Late Paleogene: First Major Diversification and Adaptive Radiation of Proboscideans". Evolution and Fossil Record of African Proboscidea. CRC Press. pp. 45–99. Sanders, William J. (2017). "Horizontal tooth displacement and premolar occurrence in elephants and other elephantiform proboscideans". Historical Biology. 30 (1–2): 137–156. Smith, Gregory James; DeSantis, Larisa R. G. (2020). "Extinction of North American Cuvieronius (Mammalia: Proboscidea: Gomphotheriidae) driven by dietary resource competition with sympatric mammoths and mastodons". Paleobiology. 46 (1): 41–57.

Prehistoric Midwest is an online science communication project started by illustrator Corbin Rainbolt. The project is composed of a series of online field guides describing prehistoric animals whose fossils are found in the Midwest About Prehistoric Midwest Prehistoric Midwest is a science communication project started by illustrator Corbin Rainbolt as a source of information about the types of ancient life and fossils which can be found in the region spanning from Ohio to North Dakota. This project is sorted into different sections focused on specific formations or moments in geologic time, detailing the types of animals found in these ancient rock layers as well as the landscapes these prehistoric organisms would have called home. Over 1000 custom illustrations have been produced for this project, and more sections will be added to this website over time as the project continues to grow! Find us on Social Media To see more of our work, follow our project's pages on social media! We often make posts to showcase new pieces of artwork or to discuss interesting aspects of Midwestern prehistory! Find us on Instagram Find us on Bluesky

Explore the different varieties of Cretaceous marine snails whose fossils are found in deposits formed by the Western Interior Sea Gastropods Aquatic Snails of the Western Interior Sea Gastropods are a group of mollusks which includes snails, slugs, sea slugs, limpets and their closest relatives. These animals are an ancestrally shelled group, although in some groups the shells have been secondarily lost or greatly reduced. In the fossil record of the Western Interior Sea, gastropod shell fossils are usually found in deposits associated with estuarine or nearshore environments and their fossils are less common than those of animals like ammonites or bivalves in areas which were further out to sea during the Late Cretaceous Anatomy Shell Structure Gastropod shells are usually formed in a spirally coiled shape and are mostly made of a mineral called calcium carbonate. The shell is structured with a series of whorls that wind around a central column called the columella. The final and largest whorl, the body whorl, holds the internal organs and most of the gastropod’s soft tissues. The smaller whorls above this large spiral together form the spire. At the tip of the shell’s spire there is a point called the apex which includes the protoconch, the earliest shell formed during the larval stage. The opening where the gastropod is able to come out of its shell is called an aperture and the shape of this opening can vary markedly between gastropod groups. The aperture is surrounded by an outer lip and a second inner lip which goes along the edge of the columella.The outside of the shells of gastropods can be covered in a lot of different types of ornamental and protective structures including ridges, grooves and even sharp spines. They also usually show a pattern of growth lines which mark the changes in the shape of the shell over time and give the snail an extra bit of structural strength. In many species the aperture of the shell is covered in a piece of hardened tissue called an operculum. (BELOW) Features of the external anatomy of the shells of gastropods using the shell of the viviparid snail Campeloma as a reference. The opening of the shell, the aperture, can usually be covered with an operculum in many genera as well. External Soft Tissues Gastropods have a soft, unsegmented body that is composed of a head section, a muscular foot, and the visceral mass. The head takes up the front-most part of the body and has one or two pairs of tentacles that these animals use to sense their surroundings. In most cases the longer set of tentacles carries the eyes either at their tips or near their bases, while the shorter tentacles are covered in touch sensors and chemical sensors. The mouth is positioned underneath these tentacles. Like in many types of mollusks, gastropods have a radula in their mouths which they used to scrape off their food. Gastropods are able to move by contracting the muscles of their foot on the lower parts of their bodies. Above this foot structure sits the visceral mass which contains most of the gastropod’s internal organs (BELOW) External soft tissue anatomy of a gastropod, in this case a terrestrial snail. The broad positions of the anatomical features in this diagram also hold true for most types of aquatic snails. (BELOW) Types of gastropod shells known from the Cretaceous period in the Western Interior Sea. The colorations and patterns shown in these images are based on those of living gastropods since the true colors of these prehistoric shelled invertebrates remains unknown in most cases. Gastropods (Browse by subclass) Subclass Caenogastropoda Family Aporrhaidae Anchura Drepanochilus Lispodesthes Family Buccinidae Aliofusus Family Cancellariidae Caveola Family Capulidae Trichotropis Family Cassiopidae Gymnentome Family Cerithiidae Cerithium Hemicerithium Levicerithium Macrocerithium Voysa Vascellum Family Cerithopsidae Monroea Family Epitoniidae Epitonium Family Fasciolariidae Bellifusus Fasciolaria Fusinus Graphidula Paleosephaea Piestochilus Family Gyrotropidae Lirpsa Family Naticidae Euspira Gyrodes Lunatia Natica Family Pseudomelaniidae Psedomelania Family Sarganidae Hillites Family Thiaridae Pyrgulifera Family Turritellidae Cragina Mesalia Turritella Caenogastropoda (continued) Family Tylostomatidae Tylostoma Family Vanikoridae Vanikoropsis Family Viviparidae Campeloma Family Volutidae Parvivoluta Tovula Subclass Heterobranchia Family Acteonidae Fictoacteon Pirsila Family Pyramidellidae Turbonilla Family Ringiculidae Cinulia Ringicula Family Siphonariidae Anisomyon Subclass Neritimorpha Family Neritidae Nerita Subclass Patellogastropoda Family Acmaeidae Acmaea Subclass Vetigastropoda Family Eucyclidae Amberleya Family Fissurelidae Diadora Family Pleurotomariidae Pleurotomaria Family Turbinidae Turbo Subclass Caenogastropoda Temporal Range: 350 million years ago - Present Habitat: Mostly aquatic, some terrestrial lineages Families in the Western Interior Sea: Aporrhaidae, Buccinidae, Cancellariidae, Capulidae, Cassiopidae, Cerithiidae, Cerithopsidae, Epitoniidae, Fasciolariidae, Gyrotropidae, Naticidae, Pseudomelaniidae, Sarganidae, Thiaridae, Turritellidae, Tylostomatidae, Vanikoridae, Viviparidae, Volutidae Caaenogastropoda is a large subclass of gastropods which accounts for more than half of all known snail species, including many aquatic animals as well as a few terrestrial lineages. Most of these animals have external shells although in a few aquatic genera had developed smaller shells enclosed within the soft tissues comprising the rest of their bodies. Some, like the viviparids, are able to live in freshwater environments. Their shells are not covered in a layer of shiny nacre and usually have an operculum. The members of this subclass usually go through a process called torsion as part of their larval stage, where their bodies are twisted around anti-clockwise such that the rear part of the animal’s body sits above their heads. They tend to have only a single pair of gill arrays. (ABOVE) Shells of gastropods of the family Aporrhaidae of the Western Interior Sea. (A) Anchura, (B)Drepanochilus, (C) Lispodesthes (ABOVE) Shell of the gastropod Aliofusus balaniformis of the family Buccinidae, found in Cenomanian deposits (ABOVE) Shell of the gastropod Caveola bellsana of the family Cancellariiidae from the Cenomanian stage (ABOVE) Shell of the gastropod Trichotropis shumardi of the family Capulidae, found in Albian deposits (ABOVE) Shell of the gastropod Gymnentome valida of the family Capulidae, found in Cenomanian deposits (ABOVE) Shells of gastropods of the family Cerithiidae of the Western Interior Sea. (A)Hemicerithium (B)Levicerithium, (C) Cerithium, (D) Macrocerithium, (E) Voysa, (F) Vascellum (ABOVE) Shell of the gastropod Monroea castellana of the family Cerithopsidae, found in Cenomanian deposits (ABOVE) Shell of the gastropod Epitonium stellanum of the family Epitoniidae, found in Cenomanian deposits (ABOVE) Shells of gastropods of the family Cerithiidae of the Western Interior Sea. (A) Graphidula (B) Fusinus, (C)Bellifusus, (D) Fasciolaria, (E) Paleosephaea, (F) Piestochilus (ABOVE) Shell of the gastropod Lirpsa cornuata of the family Gyrotropidae, found in Cenomanian deposits (ABOVE) Shells of gastropods of the family Naticidae of the Western Interior Sea. (A) Natica, (B) Gyrodes, (C)Lunatia, (D) Euspira (ABOVE) Shell of the gastropod Pseudomelania ferrata of the family Pseudomelaniidae, found in Cenomanian deposits (ABOVE) Shell of the gastropod Hillites multilirae of the family Sarganidae, found in Cenomanian deposits (ABOVE) Shell of the gastropod Pyrgulifera costata of the family Thiaridae, found in Cenomanian deposits (ABOVE) Shells of gastropods of the family Turritellidae of the Western Interior Sea. (A) Craginia, (B) Mesalia, (C)Turritella (ABOVE) Shell of the gastropod Tylostoma elevata of the family Tylostomatidae, found in Albian deposits (ABOVE) Shell of the gastropod Vanikoropsis nebrascensis of the family Vanikoridae, found in Campanian deposits (ABOVE) Shell of the gastropod Campeloma nebrascensis of the family Vanikoridae, found in Maastrichtian deposits (ABOVE) Shells of gastropods of the family Volutidae of the Western Interior Sea. (A) Tovula, (B) Parvivoluta Gallery: Caenogastropoda - click to expand images Subclass Heterobranchia Temporal Range: 409 million years ago - Present Habitat: Includes most terrestrial snails and slugs as well as some aquatic snails Families in the Western Interior Sea: Acteonidae, Pyramidellidae, Ringiculidae, Siphonariidae Heterobranchia is a subclass of gastropods which includes most of the more familiar types of land snails and slugs, along with aquatic sea slugs and sea hares. The group was once further subdivided into the Opisthobranchs, a diverse group of aquatic snails which included bubble shells and nudibranchs, and the Pulmonates, which included most land snails as well as some aquatic forms. Today the classification of heterobranchs is somewhat more complicated and a lot of animals have now been moved over to an informal classification called “Lower Heterobranchia”. Most land snails and sea slugs are now part of the infraclass Ethyneura. (ABOVE) Shells of gastropods of the family Acteonidae of the Western Interior Sea. (A) Fictoacteon (B) Pirsila (ABOVE) Shell of the gastropod Turbonilla of the family Pyramidellidae (ABOVE) Shells of gastropods of the family Ringiculidae of the Western Interior Sea. (A) Cinulia (B) Ringicula (ABOVE) Shell of the gastropod Anisomyon borealis of the family Siphonariidae, found in Campanian deposits Gallery: Heterobranchia - click to expand images Subclass Neritimorpha Temporal Range: 484 million years ago - Present Habitat: Mostly aquatic, some terrestrial lineages Families in the Western Interior Sea: Neritidae Neritimorpha is a subclass of snails which includes both aquatic and terrestrial lineages. In many of these animals inner walls of the parts of the shell left behind from their larval stages in the form of the protoconch are resorbed once the snails mature. In species who have an operculum, these structures are composed mostly of calcium-based material. Their shells often tend to be rather short with the upper parts of their spires appearing reduced. (ABOVE) Shell of the gastropod Nerita ornata of the family Neritidae, found in Cenomanian deposits Gallery: Neritimorpha - click to expand images Subclass Patellogastropoda Temporal Range: 450 million years ago - Present Habitat: Aquatic, attached to surfaces Families in the Western Interior Sea: Acmaeidae The subclass Patellogastropoda is an unusual group of gastropods, often known by the common name “true limpets” who anchor themselves to hard surfaces and have wide, shallow, cone-shaped shells. In many types of true limpets the outer shape of the shell spiral is lost and these animals instead have long, thin ridges running from the tallest part of the shell to its outer edges. Other true limpets have smooth shells. (ABOVE) Shell of the gastropod Acmaea pilleolus of the family Acmaeidae, found in Cenomanian deposits Gallery: Patellogastropoda - click to expand images Subclass Vetigastropoda Temporal Range: 421 million years ago - Present Habitat: Aquatic Families in the Western Interior Sea: Eucyclidae, Fissurelidae, Pleurotomariidae, Turbinidae The subclass Vetigastropoda is a group of aquatic snails which includes keyhole limpets, abalones and turban shells. They seem to be one of the most basal groups of snails. Some members of this group closely resemble limpets, although they are not very closely related to true limpets in the subclass Palletogastropoda. These keyhole limpets can be distinguished from true limpets by the opening on the tops of their shells. Other genera have spiral-shaped shells which range in shape from taller conical forms to shorter, more compressed or dome-shaped forms. They usually have an operculum which covers their shell apertures. (ABOVE) Shell of the gastropod Amberleya mudgeana of the family Eucyclidae, found in Albian deposits (ABOVE) Shell of the gastropod Diadora bartonvillensis of the family Fissurelidae, found in Albian deposits (ABOVE) Shell of the gastropod Pleurotomaria austinensis of the family Pleurotomariidae, found in Cenomanian deposits (ABOVE) Shell of the gastropod Turbo serratus of the family Turbinidae found in Cenomanian deposits Gallery: Vetigastropoda - click to expand images Suggested References: Gastropods Selden, P. A., ed. (2009). “Treatise on Invertebrate Paleontology. Part L, Mollusca 4, Revised, vol. 2.” The University of Kansas Paleontological Institute. Lawrence, Kansas Stephenson, L.W., & Stenzel, H.B. (1952). Larger invertebrate fossils of the Woodbine formation (Cenomanian) of Texas, with Decapod Crustaceans from the Woodbine formation of Texas. Digital Atlas of Ancient Life. (n.d.). “Gastropoda”. Cretaceous Atlas of Ancient Life | Gastropoda. https://www.cretaceousatlas.org/classes/gastropoda/ Everhart, M.J. (2017). “Oceans of Kansas - A Natural History of the Western Interior Sea, Second Edition”. Indiana University Press, 460 pp. Brinster, K. F. (1970). “Molluscan Paleontology of the Pierre Shale (Upper Cretaceous), Bowman County, North Dakota (MS)”. University of North Dakota.

An illustrated guide to the Cretaceous bivalves of the Western Interior Sea including rudists and giant inoceramid clams. Bivalves Clams, Mussels, and Oysters Bivalves are a class of mollusks whose bodies are enclosed within two shells or valves. These animals have specialized gill structures which are also used to grab ahold of food to help them filter feed. Their shells are mostly made of calcium carbonate but in some animals, elements of their shells are occasionally composed of other minerals, such as aragonite. The two halves of the body of the bivalve are joined at a point called a hinge which is fastened by a strong ligament which allows the shells to open and close. In many types of bivalves, a large lower soft tissue element called a foot protrudes outside of the animal’s valves and can be used to burrow or to help the bivalve move along the seafloor. Bivalves are also some of the oldest groups of extant invertebrates and their fossil record stretches all the way back to the early Cambrian period. Anatomy Shell Structure Bivalves have two hard shells, or valves, connected along their dorsal margins by a hinge mechanism. The hinge includes a ligament and a series of interlocking teeth that keep the valves aligned while allowing them to open and close. Powerful adductor muscles are attached to the inner shell surface, and their points of attachment leave oval-shaped scars on each side of the shell. Between these scars there is a shallow groove on the inside of the shell called the pallial line. This line marks the edge of the internal soft mantle of the bivalve. The shell itself is built from a series of layers, each with their own particular composition. The outer protective covering, known as the periostracum, is built from a protein called conchiolin and shields the shell from environmental wear and chemical damage. Beneath this is the main structural part of the shell, composed of calcium carbonate. In some species, the innermost layer of the shell is made of a substance called nacre, which makes the inside of the shell appear iridescent. The outside surface of the shell is usually marked by a series of concentric growth lines. The outer shell can further be covered in vertical ribs, like those seen in scallops. Along the dorsal edge of each valve the oldest area on the shell and the first growth rings surround a small elevated point called the umbo, which is usually positioned above the hinge of the bivalve. Shell Variation Bivalves in the Western Interior Sea came in many forms, some of which would be familiar to our eyes, while other extinct groups would seem very strange to us. Among the most distinctive bivalves found in these ancient environments were the rudists, a group of bivalves which were unique to the Mesozoic era and whose shells were shaped like cylinders, cones or crescents. Rudists were some of the main reef-building animals during the Cretaceous period. Fossilized corals are rather rare in deposits from the Interior Sea but we have a huge array of fossils representing large accumulations of rudist colonies along parts of the seafloor. Inoceramid clams would also have been a common sight in these ancient seaways, some of which could grow to be more than eight feet wide. Most of these unique bivalve groups went extinct at the end of the Cretaceous period but many groups whose fossils are known from Cretaceous rocks, such as the true mussels, cockles, ark clams and oysters, managed to survive to the present day. Most bivalves are suspension feeders but the exact shapes of their shells are determined by their strategies for catching food. Some bivalves are somewhat mobile and can move along the seafloor in search of places to burrow. Others are completely stationary and will cement themselves to rocks, driftwood or other types of harder substrates, even forming reef-like colonies of thousands of bivalves living in the same area. Bivalves (Browse by order) Order Adapedonta Leptosolen Panope Panopea Siliqua Superorder Anomalodesmata Anatyma Cuspidaria Geniomya Laternula Pholadomya Psilomya Order Arcida Breviarca Cuculea Idonearca Limopsis Parallelodon Protarca Order Cardiida Callistina Cardium Cyclorisma Nelltia Protocardia Protodonax Solyma Tancredia Tellina Tellinimera Trachycardium Order Carditida Crassatella Opis Venericardia Order Hippuritida Durania Eoradiolites Hippurites Proradiolites Sauvagesia Order Lucinida Clissocolus Ctena Lucina Nympholucina Sexta Order Myalinida Cremnoceramus Inoceramus Myalinida Mylitoides Volviceramus Order Myida Caryocorbula Corbula Opertochasma Parmicorbula Pholas Ursirivus Order Mylitida Brachidontes Botula Crenella Lithophaga Modiolus Volsella Order Nuculanida Malletia Nuculana Yoldia Order Nuculida Acila Nucula Order Ostreida Crassostrea Exogyra Gervilliopsis Gryphaea Lopha Nanostrea Pseudoperna Pycnodonte Tenuipteria Texigryphaea Order Pteriida Phelopteria Pteria Order Pectinida Anomia Lima Pecten Plicautula Neithea Syncyclonema Order Solemyida Solemya Order Trigoniida Trigonia Order Venerida Arctica Callistina Corbicula Cyclorisma Cyprimeria Dentonia Flaventia Legumen Adapedonta Temporal Range: 460 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Burrowers, mobile Adapedonta is the order which includes today’s razor clams. They are typically found in saltwater environments and many species prefer to live very close to the shoreline. They often burrow into the sand using the “foot” section of their bodies, while it uses its siphon to pull in water and food. Their diets are primarily composed of plankton. Most members of this order have long, thin shells or oval/trapezoidal shells. (ABOVE) Cretaceous bivalves of the order Adapedonta: A. Panopea , B. Panope, C. Siliqua , D. Leptosolen Gallery: Adapedonta - click to expand images Anomalodesmata Temporal Range: 480 million years ago - Present Diet: Suspension feeder, plankton, algae, occasionally copepods Lifestyle: Stationary and mobile forms, some are burrowers The superorder Anomalodesmata is best represented in the Cretaceous fossil record of the Western Interior Sea by the members of the family Laternulidae, also known as the lantern clams, as well as the superfamily pholadomyoidea. These animals share some basic behavioral similarities with razor clams, as they sit below the substrate of the seafloor with their siphons exposed above the sand or muddy surface in order to draw in food. Lantern clams have long, thin, roughly oval-shaped shells whose umboes protrude somewhat from the surfaces of the valves around the hinges. In living genera the outsides of the shells of these bivalves are usually mostly white in color, occasionally with some darker spots. (ABOVE) Cretaceous bivalves of the superorder Anomalodesmata, A. Anatymia , B. Laternula , C. Geniomya , D.Cuspidaria, E. Pholadomya , F. Psilomya Gallery: Anomalodesmata - click to expand images Arcida Temporal Range: 484 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Stationary and mobile forms, some are burrowers Arcida is the order of bivalves which includes ark clams, false ark clams and bittersweets. The outside texture of their valves varies widely between families. Limopsids have mostly smooth outer valve surfaces, ark shells and their relatives have horizontal ridges running along the outsides of their valves, and parallelodontids have vertical ridges on their shells. These animals are mostly found in saltwater environments. Some are capable of forming burrows. (ABOVE) Cretaceous bivalves of the order Arcida, A. Breviarca , B. Idonearca , C. Cucculea , D. Parallelodon , E. Protarca , F. Limopsis Gallery: Arcida - click to expand images Cardiida Temporal Range: 450 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Stationary and mobile forms, some are burrowers Cardiida is the order of bivalves which includes cockles, bean clams, wedge shells, tellin clams, and venus clams. Their shells vary in shape, some are oval, some are heart-shaped, others, as with many bean clams, are almost triangular. They are usually smooth with some families exhibiting some very faint horizontal ridges on the outsides of their valves, but others can have very prominent vertical ribs similar to those of scallops, as is the case with many cockles. Members of this genus prefer saltwater habitats but some are found very near the shoreline. (ABOVE) Cretaceous bivalves of the order Cardiida, A. Trachycardium, B. Cardium, C. Sourimis, D. Cyclorisma, E. Protocardia, F. Tancredia, G. Linearia, H. Nelltia, I. Solyma, J. Tellinimera, K. Callistina, L. Tellina, M. Protodonax Gallery: Cardiida- click to expand images Carditida Temporal Range: 480 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Mobile, some are burrowers Cariditida is an order of bivalves usually found in marine habitats. Members of this order have rounded, trapezoidal or triangular shells. Some members of this group have smooth shells or shells with strong horizontal or concentric ribbing. Members of the family Carditidae have very strong vertical ribbing which makes them appear very similar to scallops. Members of this group are often fairly mobile and some are capable of forming burrows. (ABOVE) Cretaceous bivalves of the order Carditida, A. Opis, B. Crassatella, C. Venericardia Gallery: Carditida- click to expand images Hippuritida Temporal Range: ~152 million years ago - 66 million years ago Diet: Suspension feeder, plankton, algae Lifestyle: Stationary, anchored to seafloor Hippuritida is an extinct order of bivalves who are better known as rudists. Rudists were bivalves who took on a distinctive tube-like shape. In many Cretaceous forms, one cylindrical or cone-shaped valve formed the lower portion of the animal’s outer body, while the other valve formed a roughly circular “lid” which covered the animal’s soft internal body. Other shapes are also known from these animals, including some whose valves would each have formed half of a crescent-shaped body plan. Some of these animals could grow to be very large, well over 4 feet across in some cases. Rudists first appear in the fossil record of the late Jurassic period and by the Cretaceous period they were abundant enough to form large reefs composed of their shells. They disappeared during the mass extinction at the end of the Cretaceous period. (ABOVE) Cretaceous bivalves of the order Hippuritida, A. Sauvagesia, B. Proradiolites, C. Hippurites, D. Durania, E. Eoradiolites Gallery: Hippuritida- click to expand images Lucinida Temporal Range: ~445 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Mobile, some are burrowers An order of bivalves which includes cleft clams and hatchet shells. Their shells are usually rounded, deep, and sometimes trapezoidal. Some families have valves which are very wide and dome-shaped. Members of this order are burrowing suspension feeders who feed on plankton. (ABOVE) Cretaceous bivalves of the order Lucinida, A. Lucina, B. Nympholucina, D. Ctena, E. Clissocolus, C. Sexta Gallery: Lucinida - click to expand images Myalinida Temporal Range: 478 million years ago - ~10 million years ago Diet: Suspension feeder, plankton, algae Lifestyle: Stationary, attached to seafloor Myalinida is an extinct order of bivalves which includes the giant inoceramid clams. Their shells are mostly smooth, although some exhibit low horizontal ridges. The largest members of this group had shells which were longer than a fully grown person. In some parts of the Niobrara Chalk formation, their shells are extremely common, although they are rarely preserved intact. (ABOVE) Cretaceous bivalves or the order Myalinida, A. Mylitoides, B. Cremnoceramus, C. Inoceramus, D. Volviceramus Gallery: Myalinida - click to expand images Myida Temporal Range: ~320 million years ago - present Diet: Suspension feeder, plankton, algae Liftstyle: Mostly stationary, some are burrowers An order of bivalves which includes shipworms, softshell clams and their relatives. They are found in saltwater habitats and are almost exclusively burrowing animals with soft, somewhat flexible shells and pronounced siphons. In some members of this group, such as shipworms, the shell is extremely reduced and most of the animal’s body is exposed. Some genera live by burrowing into driftwood. (ABOVE) Cretaceous bivalves of the order Myida, A. Ursirivus, B. Corbula, C. Caryocorbula, D. Parmicorbula, E. Pholas, F. Opertochasma Gallery: Myida - click to expand images Mytilida Temporal Range: ~480 million years ago - present million years ago Diet: Suspension feeder, plankton, algae Lifestyle: Stationary Mytilida is an order of bivalves which includes sea mussels and all true mussels. They have valves which are somewhat asymmetrical and attach themselves to rocks or other surfaces using a web of filamentous structures called a byssus. They often form in large groups where substrates permit them to do so and they are found in both marine and estuarine habitats. Most of their shells are oval or otherwise elongated in their shape. (ABOVE) Cretaceous bivalves of the order Mytilida, A. Volsella, B. Crenella, C. Modiolus, D. Brachidontes, E. Lithophaga, F. Botula Gallery: Mytilida - click to expand images Nuculanida Temporal Range: 485 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Mobile, most are burrowers Nuculanida is an order of small saltwater clams. Many members of this group are less than a centimeter long. They tend to have smooth, elongated shells which are either oval or trapezoidal in shape. Their shells are thin-walled and composed of the mineral aragonite. Some smaller forms appear translucent and may have an iridescent appearance. (ABOVE) Cretaceous bivalves of the order Nuculanida, A. Malletia, B. Yoldia, C. Nuculana Gallery: Nuculanida - click to expand images Nuculida Temporal Range: ~480 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Mobile, slow-moving Nuculida is an order of small saltwater clams which includes nut clams and their closest relatives. Many members of this group are very good burrowers and tend to live in areas with very fine sand or mud on the seafloor. Their shells are rounded, oval-shaped, or nearly triangular with rounded edges. Some genera have ornamentation on the outsides of their valves, horizontal ridges and/or vertical ribs, which can sometimes give their outer surfaces a crosshatched appearance. Most of their shells have a layer of nacre on the inside. (ABOVE) Cretaceous bivalves of the order Nuculida, A. Nucula, B. Acila Gallery: Nuculida - click to expand images Ostreida Temporal Range: ~480 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Stationary, cemented to rocks, wood or substrate Ostreida is the order of bivalves which includes true oysters and honeycomb oysters. The outsides of their valves usually have a rough bark-like texture. Bivalves in this order tend to grow with their shells cemented to a hard surface, such as a rock, a larger shell or a piece of driftwood. Large groups of these animals can form coastal reefs. (ABOVE) Cretaceous bivalves of the order Ostreida, A. Crassostrea, B. Gervillia, C. Ostrea, D. Lopha, E. Texigryphea, F. Pycnodonte, G. Gervilliopsis, H. Nanostrea, I. Gryphaea, J. Pseudoperna, K. Pseudoptera, L. Exogyra, Tenuipteria Gallery: Ostreida - click to expand images Pectinida Temporal Range: ~470 million years ago -Present Diet: Suspension feeder, plankton, algae Lifestyle: Stationary, most attach themselves to substrate or to solid objects Pectinida is an order of bivalves which includes most types of animals commonly referred to as scallops as well as kittenpaws and jingleshells. These animals live in both brackish and saltwater habitats. Most extant members of this group are able to attach themselves to a substrate but some Cretaceous members of this order are unable to do so. In some families, namely the true scallops, the outsides of the shells are covered in very pronounced vertical ribs. Other groups, like jingleshells, have smoother shells or shells with an uneven pavement of divots and ridges. (ABOVE) Cretaceous bivalves of the order Pectinida, A. Lima, B. Pecten, C. Neithea, D. Anomia, E. Syncyclonema, F. Plicautula Gallery: Pectinida - click to expand images Pteriida Temporal Range: ~460 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Stationary, cemented to rocks, wood or substrate Pteriida is an order of bivalves which includes pearl oysters and pen shells. The bivalves in this group come in many different shapes. Some have long, thin shells shaped like flattened cones, others have long wing or spike-like projections on the outsides of their valves near their hinges. Like the bivalves in the order Ostreida, these bivalves attach themselves firmly to the seafloor by cementing themselves beside rocks or the outsides of larger shells. (ABOVE) Cretaceous bivalves of the order Pteriida, A. Phelopteria, B. Pteria Gallery: Pteriida- click to expand images Solemyida Temporal Range: 483 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Mobile The order Solemyida includes the bivalves commonly known as awning clams. Their shells are usually long and oval in shape and they are found in both shallow and deep water marine habitats. The members of this group are typically burrowing bivalves who are able to tunnel into soft substrate using an enlarged lower foot structure. Some members of this order have shells with shallow vertical ribs issuing outwards from the area around the umbo. (ABOVE) Cretaceous bivalves of the order Solemyida, A. Solemya Trigoniida Temporal Range: ~415 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Mobile Trigoniida is an order of marine saltwater clams whose members have a lot of variation in their shapes and ornamentation. Some members of this order are superficially similar to scallops, with several families known to have pronounced vertical striations along their shells. The hinge teeth of many of the members of this order are particularly elaborate. In some extinct genera, one larger valve will encompass the second smaller valve. The members of this group were mostly known from fossil material until the discovery of living examples of Trigoniid clams off the coast of Australia during the 19th century. (ABOVE) Cretaceous bivalves of the order Trigoniida, A. Trigonia Gallery: Trigoniida - click to expand images Venerida Temporal Range: ~450 million years ago - Present Diet: Suspension feeder, plankton, algae Lifestyle: Mobile Venerida is an order of clams which includes animals which are found in both saltwater and freshwater habitats. Members of this group include venus clams, duck clams and kelly clams. They tend to have smooth shells with limited ornamentation aside from their growth lines. Their shells are usually oval or trapezoidal in shape. (ABOVE) Cretaceous bivalves of the order Venerida; A. Callistina, B. Flaventia, C. Cyclorisma, D. Sinonia, E. Legumen, F.Cyprimeria, G. Dentonia, H. Arctica, I. Corbicula Gallery: Venerida - click to expand images Suggested References: Bivalves Cox, L. R. et al. (1969). “Bivalvia”, in R. C. Moore ed., Treatise on Invertebrate Paleontology, Part N, Mollusca 6, Volume 2. The University of Kansas and Geological Society of America. 1224 pp. Crampton, J.S. (2004). “Shell composition, cryptic costae, complex composite molds and taphonomic chicanery in Mytiloides (Inoceramidae, Bivalvia).” Journal of Paleontology 78(6):1091-1096. Digital Atlas of Ancient Life. (n.d.). “Bivalvia”. Cretaceous Atlas of Ancient Life | Bivalvia. https://www.cretaceousatlas.org/classes/bivalvia/ Everhart, M.J. "Inoceramids" Oceans of Kansas website: http://oceansofkansas.com/Inoceramids.html Everhart, M.J. (2017). “Oceans of Kansas - A Natural History of the Western Interior Sea, Second Edition.” Indiana University Press, 460 pp. Selden, P. A., ed. (2009). “Treatise on Invertebrate Paleontology. Part L, Mollusca 4, Revised, vol. 2.” The University of Kansas Paleontological Institute. Lawrence, Kansas Hattin, D. E. (1988).” Rudists as historians; Smoky Hill Member of Niobrara Chalk (upper Cretaceous) of Kansas”, Fort Hays Studies, Third Series, 10:4-22. Henderson, R. (2004). “A Mid-Cretaceous association of shell beds and organic-rich shale: Bivalve exploitation of a nutrient-rich, anoxic sea-floor environment.” Palaios, 19(2):156-169. Stephenson, L.W., & Stenzel, H.B. (1952). Larger invertebrate fossils of the Woodbine formation (Cenomanian) of Texas, with Decapod Crustaceans from the Woodbine formation of Texas. Stewart, J.D. (1990). “Niobrara Formation symbiotic fish in inoceramid bivalves. p. 31-41 In S. Christopher Bennett (ed.), 1990 Society of Vertebrate Paleontology Niobrara Chalk excursion guidebook”. Museum of Natural History and the Kansas Geological Survey, Lawrence, Kansas

Explore the environments and habitats found in the Pleistocene epoch of the Midwest, including grasslands, forests and tundras The Landscape of the Pleistocene (ABOVE) Glaciers and ice sheets advancing across the Midwest had a profound impact on the surrounding landscape. Outwash plains on the outer margins of ice sheets were covered in braided streams and small kettle lakes. A Land of Ice Sheets, Prairies and Forests During the Pleistocene epoch the Midwest was dramatically shaped by repeated advances and retreats of continental glaciers. Massive ice sheets, sometimes more than a mile thick, covered much of the region, carving the landscape and transporting enormous amounts of rock, sand, gravel, and clay. As the glaciers moved, they eroded bedrock and deposited sediments that later formed fertile plains, rolling hills, and moraines. The Great Lakes began to take shape as glacial ice deepened existing river valleys and left behind basins that filled with meltwater. The environment of the Midwest changed repeatedly in response to the shifting climate. During colder periods, tundra and boreal forests dominated the landscape. These environments supported animals adapted to harsh conditions. Mammoths, mastodons, giant ground sloths, and other large mammals roamed across open grasslands and woodlands. As glaciers retreated during warmer intervals, forests expanded and diverse plant communities developed. Meltwater from the ice sheets created extensive rivers, lakes, and wetlands. Forests and Wetlands (ABOVE) Pleistocene woodlands were often found near rivers and wetland habitats and were home to many types of browsing and semi-aquatic mammals. Cervalces (1), Castoroides (2), American mastodon (3) Pleistocene forested environments in the Midwest occurred primarily during warmer interglacial periods and in sheltered areas near rivers, lakes, and wetlands. These forests varied from northern boreal woodlands dominated by evergreen trees to mixed deciduous forests containing oak, maple, and aspen trees. The composition and extent of these forests shifted repeatedly as climatic conditions changed with the advance and retreat of the ice sheets which dominated much of the higher latitudes of North America. Pleistocene woodlands supported a diverse assemblage of mammals. Mastodons were among the most characteristic forest inhabitants, browsing on twigs, leaves, shrubs, and wetland plants rather than grazing on grasses like mammoths. White-tailed deer, moose, and ancient peccaries like Platygonus also occupied forest habitats. (ABOVE) Many forest habitats in parts of Kansas and Nebraska may have been composed of large clusters of aspen trees, similar to those seen in parts of the American west today. Photo credit: Lisa Kennedy, US Forest Service (ABOVE) A pine forest growing along the edge of a stream in the Yukon. These types of forests may have grown alongside more open tundras in areas where water was regularly available, near glacial braided streams for example. Photo credit: Kristine Sowl, USFWS, YDNWR Grasslands (ABOVE) Grazing animals would have been common sights in the Pleistocene grasslands of the Midwest. These included the extinct pronghorn Stockoceros (1), The columbian mammoth (2), and the giant bison (3) Grasslands and prairies covered extensive portions of the Midwest during the Pleistocene. These open landscapes supported a rich community of plants and grazing animals adapted to seasonal climate extremes. Both tallgrass and shortgrass prairies were present in different areas during this epoch, with the types of floral communities being heavily dependent upon the average yearly temperature and the amount of rainfall present within a given area. Some grassland environments closely resembled savannah environments, with patches of burr oak trees and other hardy plants surrounded by expanses of open grass. Relatives of today’s bluestem grasses had existed in the Midwest since around the Miocene epoch and remained an important part of these Pleistocene grasslands and prairies. The vegetation was dominated by hardy grasses, sedges, and herbaceous flowering plants capable of surviving cold winters and periodic drought. Among the most notable grassland animals were mammoths, whose flat tooth surfaces were adapted for chewing and processing grasses and tougher silicate-rich plant materials. Pleistocene communities of large grazing mammals also included ancient bison, horses and camels, all of which fed on grasses and other low-growing herbaceous vegetation. (ABOVE) The landscape of the Flint Hills in eastern Kansas. These types of tallgrass prairies would have been found in warmer parts of the Midwestern region during the Pleistocene, home to many types of wildflowers and bluestem grasses. Photo credit: Greg Kramos/USFWS Tundras (ABOVE) Pleistocene animals found in tundra habitats included the saber-toothed cat Homotherium (1) and the woolly mammoth (2) During the Pleistocene epoch, parts of the Midwest near the edges of the Laurentide ice sheets supported many tundra environments. These landscapes were cold, windy, and relatively dry, with few trees and large expanses of short grasses and cold-resistant plants. Beneath the ground there were layers of permanently frozen soil known as permafrost. These tundra environments in the northern Midwest were home to populations of woolly mammoths, as well as herds of the extant genus of muskox, Ovibos. (ABOVE) Tundra environments are open areas covered in short grasses and sedges with a thick layer of permafrost beneath the surface layer of earth. Although they're found in polar areas today, they once could be found along the margins of ice sheets which extended deep into North America during the Pleistocene epoch. Photo credit: U.S. Fish and Wildlife Service The Legacy of the Ice Sheets Many parts of the Midwest were once covered by the Laurentide Ice Sheet, a continental glacier that advanced southward from the area around the Hudson Bay region during repeated glacial periods. At its greatest extent, the ice covered nearly all of the upper Midwest, leaving only a few areas untouched by direct glaciation, namely the Driftless Area of Wisconsin, Minnesota, Iowa, and Illinois. The region near the glacier's edge was characterized by cold tundra and steppe-tundra environments, while braided streams and temporary glacial lakes formed along the ice margin. (BELOW) A map of the Midwest as it appeared during the last ice age. As the Laurentide ice sheet retreated it gouged deep troughs into the ground and widened pre-existing valleys, eventually forming what we now know as the Great Lakes As the ice advanced, it profoundly altered the landscape. The moving glaciers scraped and polished bedrock, carved grooves known as glacial striations, smoothed hills, filled valleys, and helped create the basins that later became the Great Lakes. When the climate warmed and the glaciers retreated, they released enormous quantities of sediment that had been carried within the ice. This material, known as glacial drift, blanketed much of the Midwest and buried older bedrock beneath thick layers of clay, silt, sand, gravel, and boulders. (BELOW) As glaciers and ice sheets retreat they leave behind distinct marks on the surrounding landscapes. Water draining through the glaciers in narrow passages called moulins can pool into lakes along the edge of the ice, drain into the bedrock below or flow outwards as streams. Moraines, eskers and kames are all formed from sediment which has been shifted or deposited by the glacier. Small depressions in the ground can collect water and form small kettle lakes. The retreating glaciers left behind many types of landforms that can be seen all across the modern Midwest. Ridges of sediment called moraines mark former ice sheet margins. Other glacial features included drumlins, kettle lakes and small hills called kames. The retreating ice sheets also reshaped drainage systems and formed thousands of small lakes and new wetland ecosystems across the northern Midwest. (ABOVE) A kettle near Ohlstadt, Germany. These small depressions are formed from blocks of ice left over as a glacier retreats. They are sometimes filled with water forming a small lake. Photo credit: Andreas Schikora (ABOVE) Glacial erratics are blocks of rock carried by glaciers as they advance. These rocks, some of which can be quite large, are later deposited elsewhere once the ice retreats. These rocks can travel hundreds of miles away from where they originated. This erratic is located near Ågestasjön, Sweden. Photo credit: Leo Johannes (ABOVE) Medial moraines formed by the Kennicott glacier in Alaska. Moraines often form along the outer edges of ice sheets and glaciers but in some cases they form along the center of a glacier, running along the length of the ice. Photo credit: Jacob W. Frank, NPS Find out more about ice age animals in the Midwest by exploring our Pleistocene field guide Learn More

Cretaceous archosaurs found in the Western Interior Sea included pterosaurs, seabirds, giant crocs and dinosaurs who had been washed out to sea. Learn more about animals like Pteranodon, Deinosuchus and Hesperornis Archosauria Dinosaurs, Crocs and Pterosaurs Archosauria is a diverse group of reptiles that includes dinosaurs, pterosaurs, crocodilians, and modern birds. Members of this clade share several key characteristics, such as openings in the skull located in front of their orbits, teeth anchored within sockets, and an upright limb posture. These features improved the mobility and efficiency of these reptiles and helped archosaurs become one of the most successful vertebrate groups of the Mesozoic era. The first Archosaurs showed up during the Triassic period and they quickly evolved into a wide variety of forms adapted to life on land, in the air and in aquatic environments. During the Cretaceous Period, the Western Interior Sea was home to a wide variety of Archosaurs. Pterosaurs flew over the seaway, while birds occupied coastal and marine habitats. Dinosaurs, including hadrosaurs and tyrannosaurs, lived along nearby shorelines and floodplains and crocodyliforms were common in rivers, estuaries, marshes and coastal regions connected to the seaway. Anatomy (ABOVE) A labeled diagram of the skull of the tyrannosauroid Gorgosaurus showing the placement of bones and key openings General Characteristics Archosaurs are a very diverse group of reptiles and as a result of the range of forms taken by the members of this group it can be difficult to find shared anatomical traits found in many living and extinct archosaurian lineages. Despite this, by looking back into the fossil record, we see that one of the key traits of the archosaurs as a group is the antorbital fenestra, an opening located in between the eye socket and nostril which helped lighten the skull. In some groups of archosaurs, such as crocodilians and birds, this fenestra was later lost. Many types of archosaurs also had a mandibular fenestra in their lower jaws, which reduced bone mass and provided additional space for jaw muscles. Their teeth are also anchored within deep sockets in the jaw. Early archosaurs also had very mobile ankles and reinforced pelvic bones which allowed them to hold themselves off the ground instead of holding a sprawled posture. (BELOW) The bones of the forelimbs of different types of archosaurs. Archosaurs ancestrally had five fingers on each hand, although only the front three fingers would have had a claw/nail. Some groups of archosaurs lost digits over time. Dinosaurs Many of the major distinguishing features which separate different groups of dinosaurs are related to the skeletal anatomies of these extinct animals. There are generally considered to be two main groups of dinosaurs; saurischians and ornithischians, which differ primarily in the arrangement of their pelvic bones. Saurischians, including theropods and sauropodomorphs, had a forward-directed pubis bone, while ornithischians evolved a pelvis in which the pubis pointed backward. Many saurischians also had hollow, lightweight bones, three-toed hind feet, and sharp teeth suited for catching and consuming prey. Some members of this group, like the sauropods, had long necks, relatively small heads, sturdy pillar-like limbs, and robust vertebrae adapted to support their immense bodies. Many saurischians seem to have had large air sacs inside of their bodies which would have helped them grow to giant sizes while remaining fairly light relative to their immense volume. It seems as though these saurischian air sacs also played a role in giving these animals more efficient ways to breathe. Ornithischians on the other hand developed several features associated with specializing in plant-eating diets, including specialized grinding teeth and in some groups an extra predentary bone at the front of the lower jaw. Some groups, such as ceratopsians, evolved horns and large frills around their skulls, whereas stegosaurs and ankylosaurs would have had protective armor and defensive skeletal structures along the length of their bodies. (BELOW) A labeled diagram of the skeletal anatomy of Gorgosaurus . The furcula, or wishbone, was present in many types of derived theropod dinosaurs by the Late Cretaceous, even in lineages which were not able to fly. Adaptations For Flight (ABOVE) Dinosaurs are usually classified as ornithischians or saurischians based on the arrangement and shape of their hip bones. Birds, which are part of the saurischian theropod group, independently developed a hip with a retroverted pubis. Various different archosaur groups independently evolved specialized skeletal features that helped them achieve powered flight. Pterosaurs, the earliest known vertebrates capable of powered flight, had wings formed by a set of membranes called patagia which stretched along an exceptionally elongated fourth finger and which were supported by thin rods called actinofibrils. Their skeletons were highly adapted for aerial locomotion, with hollow lightweight bones that minimized body weight without sacrificing structural strength. Birds, descendants of maniraptoran theropod dinosaurs, developed an alternative wing design in which feathers attached to modified bones in their forelimbs. Over time they evolved several new flight-related adaptations, including a fused clavicle, or furcula (the wishbone), and a large keeled sternum that anchored large flight muscles developed from the pectoral muscles around the chest. Fusing different bones was a common strategy in different types of flying archosaurs. In pterosaurs for instance, many of the thoracic vertebrae became linked together into a rigid bony structure called a notarium. Many of these animals also had fused synsacra composed of their fused or semi-fused sacral vertebrae. (BELOW) In order to deal with the skeletal stresses required for a bird to develop powered flight, these animals evolved a suite of anatomical characteristics which gave them more support for their flight muscles. This includes the extra large sternal keel. Some ancient seabirds would have had some unique anatomical features not seen in today's birds. For instance, many Cretaceous seabirds would have had teeth lining their bills, similar to the serrations seen on the beaks of living mergansers, likely an adaptation for catching slippery prey. (BELOW) A series of diagrams with labels showing the skeletal anatomy of the pterosaur Pteranodon sternbergi . Note the fusion of the thoracic vertebrae into a notarium and the fused sacral vertebrae which have formed a synsacrum. (BELOW) The bones of the wings of Pteranodon and their corresponding equivalents in the bones of a human arm. The second half of a pterosaur's wing is built from the bones of the 4th finger. The wing membranes of these animals were held in place by a series of strong soft tissue structures called actinofibrils which became more densely packed towards the wingtip Aquatic Adaptations Ancient archosaurs didn't just take over the land and manage to evolve powered flight, some groups also became partially or fully aquatic. Many crocodylomorph groups evolved streamlined body shapes that reduced water resistance and enhanced swimming ability. Long, narrow jaws lined with sharp teeth were particularly effective for capturing fish and other aquatic prey. The placement of the eyes and nostrils high on the skull allowed these animals to remain largely submerged while still being able to see and breathe at the water’s surface. Adaptations of the limbs also played an important role in the transition to the water, and some forms developed paddle-like appendages that gave them extra propulsion while swimming, although most of these animals depended primarily on their tails to push themselves forward. Among the most specialized marine crocodylomorphs, such as metriorhynchids, further modifications included flipper-like limbs, reduced osteoderms, and powerful tail fins adapted for sustained swimming in open seas. Some groups even developed specialized salt glands which allowed these animals to process saltwater, a trait which is also found in many of today’s living crocodiles. (ABOVE) The crocodylomorph Terminonaris is an example of a type of archosaur which became adapted to spending life at sea. Many anatomical features associated with today's crocodilians appeared independently at many points during the evolutionary history of crocodylomorphs as different lineages of these animals repeatedly moved into aquatic niches Archosaurs Non-avian dinosaurs Claosaurus Niobrarasaurus Birds (Class Aves) Apatornis Baptornis Fumicollis Guildavis Hesperornis Iaceornis Ichthyornis Parahesperornis Pasquiaornis Pterosaurs (Order Pterosauria) Aetodactylus Alamodactylus Cimoliopterus Nyctosaurus Pteranodon Clade Crocodylomorpha Deinosuchus Terminonaris Non-Avian Dinosaurs (Dinosauria) Dinosaurs Preserved at Sea The term “non-avian dinosaurs” is used to refer to all dinosaurs except for the group which includes today’s birds and their closest extinct bird relatives. Most non-avian dinosaur fossils found in rocks left behind by the Western Interior Sea are the remains of animals that were washed out to sea. Two of the most notable cases of this type of fossilization are the fossils of Niobrarasaurus and Claosaurus . Niobrarasaurus was a nodosaurid ankylosaur, a heavily built, four-legged herbivore protected by rows of bony armor plates called osteoderms. Unlike some other ankylosaurs, it lacked a tail club and likely relied on its thick armor and defensive shoulder spines for protection. Claosaurus , in contrast, was a slender early hadrosauromorph closely related to the duck-billed dinosaurs. It had small forelimbs, an elongated tail, long hind limbs, and a lightweight body adapted for efficient movement. Claosaurus did not have any dermal armor covering its skin and would have had simpler teeth than more advanced hadrosaurs. Claosaurus Temporal Range: 87 million years ago - 82 million years ago Geographic Range: Kansas Species: C. agilis Diet: Herbivorous browser, ferns, leaves, leaf buds Claosaurus was among the first dinosaur genera to be discovered in the Niobrara Formation of western Kansas. The fossil remains were collected by Othniel Charles Marsh in 1871 near the Smoky Hill River and were originally described in 1872 as Hadrosaurus agilis . As additional material became available and the specimen was studied more closely, Marsh determined that it differed significantly from Hadrosaurus and established the new genus Claosaurus in 1890. Fossils attributed to Claosaurus include portions of the skull, vertebral column, ribs, limb bones, and pelvic elements. These remains have made the genus an important subject in studies of hadrosauromorph evolution because it represents an early relative of the more specialized duck-billed dinosaurs that also lived during the Cretaceous. The occurrence of Claosaurus fossils in marine chalk deposits is particularly noteworthy because the animal lived on land. During the Late Cretaceous, much of present-day Kansas was submerged beneath the Western Interior Seaway. After this particular Claosaurus died its remains were likely transported from a nearby coastal region into the seaway, where they settled on the sea floor and became buried in fine carbonate sediments. Over millions of years, these sediments lithified into the chalk deposits of the Smoky Hill Member, preserving the remains of this terrestrial dinosaur in an otherwise marine environment. (BELOW) A photo of the mounted remains of Claosaurus agilis at the Yale Peabody Museum. Photo credit: user Greygirlbeast, accessed via Wikimedia Commons, distributed under a CC BY-SA 3.0 license (BELOW) Most of the skull is missing from the holotype specimen of Claosaurus . It is usually restored with a skull shape similar to that of animals like Eotrachodon , with a wide beak at the front of the mouth and large chewing tooth batteries Niobrarasaurus Temporal Range: 87 million years ago - 82 million years ago Geographic Range: Kansas Species: N. coleii Diet: Herbivorous browser, ferns, leaves, leaf buds Niobrarasaurus was an armored herbivorous dinosaur belonging to the nodosaurid branch of the ankylosaurs. Its body was covered with osteoderms, or bony plates, embedded within the skin, which formed a protective shield against predators. Unlike ankylosaurids such as Ankylosaurus , Niobrarasaurus did not have a tail club. Instead, it likely depended on its heavy body armor and on the enlarged defensive spines along its shoulders and the sides of the body for protection. The dinosaur walked on four sturdy legs and was adapted for a life spent browsing on low-growing vegetation. Scientific study of Niobrarasaurus began in 1930 when geologist Virgil Cole discovered a collection of fossil remains in western Kansas. The specimen was formally described in 1936, and was named Hierosaurus coleii. Decades later, paleontologists reexamined the fossils and concluded that they represented a distinct genus, later named Niobrarasaurus in 1995. (BELOW) The skeleton of Niobrarasaurus, MU 650 VP, on display at the Sternberg Museum of Natural History in Hays, Kansas. These fossils were found in Gove County, Kansas and are one of only a few non-avian dinosaur remains to have been found in the state. This image shows the reconstructed skull, forelimb bones and the osteoderms of the front of the body, (BELOW) The skeleton of Niobrarasaurus, MU 650 VP, middle section showing the ribs, osteoderms of the middle of the trunk (BELOW) The skeleton of Niobrarasaurus, MU 650 VP, this photo is of the rear section of the skeleton and shows the pelvis, hind limbs, rear osteoderms and caudal vertebrae of the animal Birds (Aves) Cretaceous Toothed Seabirds The Western Interior Sea was home to many types of marine birds. Unlike many of today’s birds, most birds from the Western Interior Sea still had small teeth lining their bills. These teeth would have been useful as tools for holding on to slippery fish, which are thought to have been the main source of food for many of these prehistoric animals. These Cretaceous birds were part of groups which were not directly ancestral to today’s birds and many of these ancient lineages would go extinct, along with the non-avian dinosaurs, at the end of the Cretaceous period. Apatornis Temporal Range: 83 million years ago Geographic Range: Kansas Species: A. celer Diet: Carnivorous, small fish, squid Apatornis was a small ornithuran bird that lived during the Late Cretaceous and is known from fossils recovered in the Smoky Hill Chalk of Kansas. Although only limited skeletal material has been discovered, the preserved remains reveal several features that distinguish it from other contemporary birds. The most important fossil consists of a synsacrum, the fused vertebrae associated with the pelvic region. Comparisons with related birds indicate that Apatorni s had at least one more sacral rib than Ichthyornis and lacked the bony tendons that reinforced the sacral region in other genera. A study of some of the material known from Apatornis published in 2004 showed that the specimen could not be confidently linked to the original material and it was reassigned to the separate genus Iaceornis. As a result our current understanding of Apatornis is based largely on a single very incomplete original fossil, and many aspects of its biology and evolutionary relationships remain uncertain. Baptornis Temporal Range: 83 million years ago - 80 million years ago Geographic Range: Kansas, Sweden Species: B. advenus Diet: Carnivorous, small fish, squid Baptornis was possibly the most specialized marine diver of all the hesperornitheans. It had a long, slender neck, heavy bones that reduced buoyancy, and extremely large and strong hind limbs that it used as its main propulsion tool while swimming underwater. Although it wasn't able to fly, its skeletal remains still preserved small, reduced wing bones. Its elongated toes and powerful legs suggest that it was an efficient swimmer that relied on underwater pursuit rather than aerial hunting. Fossils of Baptornis were found fairly early on in the history of Kansas paleontology. Their remains were described In 1877. Because it was among the earliest fossil birds discovered from the Mesozoic Era, Baptornis became an important animal in studies of avian evolution. Additional specimens collected throughout the twentieth century revealed much more of its skeleton and allowed researchers to reconstruct its aquatic lifestyle, anatomy, and evolutionary relationships. Fumicollis Temporal Range: 85 million years ago Geographic Range: Kansas Species: F. hoffmani Diet: Carnivorous, small fish, squid Fumicollis belonged to the group of flightless diving birds known as hesperornitheans. Its fossil remains were first collected in 1937 from the Smoky Hill Member of the Niobrara Chalk in Kansas by Harold Shepherd and George Sternberg. For many years, the specimen was classified as belonging to the diving bird genus Baptornis. Subsequent research determined that these fossils displayed some unique features, including enlarged processes on the vertebrae and unusually elongated pelvis, which suggested that the animal was distinct from Baptornis and other known hesperornitheans. Following a detailed reexamination of the material, paleontologists Alyssa Bell and Luis Chiappe named the new genus and species Fumicollis hoffmani in 2015. Guildavis Temporal Range: 83 million years ago Geographic Range: Kansas Species: G. tener Diet: Carnivorous, small fish, squid Guildavis was a small bird that lived during the Late Cretaceous and is known from fossils recovered from the Niobrara Chalk Formation of Kansas. Although the available fossil material is limited, the genus appears to represent a distinct lineage of early ornithuran birds, the group that includes modern birds and their close relatives. The most important fossils consist of portions of the synsacrum, the fused vertebrae that support the pelvic region. It has at various times been considered to be a synonym of Ichthyornis. Hesperornis Temporal Range: 83 million years ago - 72 million years ago Geographic Range: Kansas, South Dakota, Alberta, parts of Russia Species: H. regalis, H. crassipes, H. gracilis, H. altus, H. rossicus, H. montana, H. bairdi, H. macdonaldi, H. mengeli Diet: Carnivorous, small prey, fish Hesperornis was a highly specialized marine bird which had completely lost its ability to fly. Its wings were greatly reduced, while its powerful paddle-like hind limbs were adapted for efficient swimming and underwater pursuit of prey. Unlike modern birds Hesperornis also had sharp teeth set within grooves in its jaws. Its streamlined body and strong legs made it an effective diver, and its lifestyle has often been compared to those of modern loons and grebes. Research on Hesperornis began in the late nineteenth century when Othniel Charles Marsh described fossils from the marine deposits of Kansas in 1872. The discovery was especially important because it revealed a bird with both avian characteristics and teeth, which in turn provided key evidence for the evolutionary connection between birds and their reptilian ancestors. Iaceornis Temporal Range: 83 million years ago Geographic Range: Kansas Species: I. marshi Diet: Carnivorous, small fish, squid Iaceornis was a small bird once considered part of the genus Apatornis . The shape of its skeleton has resulted in this genus being placed in a position in between earlier birds such as Ichthyornis and the ancestors of modern birds. Its wing bones have more in common with wings of living birds than the wing anatomies seen in many of its contemporary Late Cretaceous species. For many decades the specimen now considered the holotype of Iaceronis was assigned to the species Apatornis celer and was widely used in descriptions of that genus. A revision of many types of Cretaceous seabirds published in 2004 determined that the wing bones of this particular specimen differed significantly from those seen in the Apatornis holotype which established Iaceornis as a new genus. Ichthyornis Temporal Range: 83 million years ago Geographic Range: Kansas, Texas, Alabama, Alberta, Saskatchewan Species: I. dispar Diet: Carnivorous, small fish, squid Ichthyornis was a seabird from the Cretaceous period that was superficially similar to a small seagull. It had sharp teeth embedded within its jaws, while the front portions of the jaws were covered by a beak. This unusual combination makes Ichthyornis one of the most important transitional birds known from the fossil record. It had a lightweight skeleton, powerful wings, and was well adapted for sustained flight over the waters of the Western Interior Sea. Othniel Charles Marsh formally described this genus in the early 1870s based on fossils found in Kansas, and the fossils quickly attracted scientific attention because they combined avian features with toothed jaws. Parahesperornis Temporal Range: 85 million years ago - 82 million years ago Geographic Range: Kansas Species: P. alexi Diet: Carnivorous, small fish, squid Parahesperornis was a flightless, toothed seabird that used its powerful hind limbs to propel itself through the water while hunting for fish. It is named for its similarities with Hesperornis and other hesperornithean birds. Fossils of the bird were first collected from the Smoky Hill Chalk of Kansas in 1894, but their significance was not immediately recognized. For many years, these remains were grouped with other hesperornithean specimens, leading to confusion about their classification. It was classified as its own genus and species in 1984. Pasquiaornis Temporal Range: 94 million years ago Geographic Range: Saskatchewan Species: P. hardiei, P. tankei Diet: Carnivorous, small fish, squid Pasquiaornis was an early member of the Hesperornithes whose remains show a combination of features that link it to both more advanced diving birds and their less specialized flying ancestors. Its limb bones and foot anatomy were adapted for swimming, but many skeletal characteristics retained a more ancestral condition than those seen in later hesperornitheans. It was originally thought to be a close relative of Baptornis but it has since been moved closer to the base of the hesperornithean family tree. There is some evidence that they might have spent time in groups since some of the original fossils found from this animal were found with many individuals located in a small area where they seem to have been deposited at around the same time. Pterosaurs (Pterosauria) Pterosaurs of the Western Interior Sea Pterosaurs were a group of Mesozoic flying reptiles and the first vertebrates to master true powered flight. They were characterized by lightweight, hollow bones, large wings made of skin membranes, and an elongated fourth finger that supported a large part of the membrane on each wing. Unlike birds, pterosaurs had wings composed of flaps of skin called patagia, superficially similar to the wing membranes of bats. Many species also displayed prominent head crests. By the end of the Cretaceous, the only remaining pterosaurs were animals with long hind legs and short tails. Many of these animals had large display crests or elaborate bill shapes. Some of the earlier Cretaceous pterosaurs of the Western Interior Sea still had teeth in their bills. Aetodactylus Temporal Range: 95 million years ago Geographic Range: Texas Species: A. halli Diet: Carnivorous, fish, squid Aetodactylu s is a small toothy pterosaur known from sites in Texas. It was discovered when a fossil lower jaw was found in 2006 near Mansfield, Texas in rocks belonging to the Tarrant Formation. In 2010, paleontologist Timothy Myers described the fossil and named the species Aetodactylus halli in recognition of its discoverer, Lance Hall. The discovery showed that certain types of toothed pterosaurs remained part of North American ecosystems even during parts of the Late Cretaceous when they had previously been considered largely extinct.The teeth of Aetodactylus seen in these snout fossils were organized with the teeth at the front of the mouth projecting forward, while the largest teeth were concentrated near the tip of the jaw and decreased in size toward the back. Unlike some ornithocheirid pterosaurs, Aetodactylus lacked a crest on its lower jaw. Alamodactylus Temporal Range: 88 million years ago Geographic Range: Texas Species: A. byrdi Diet: Carnivorous, fish, squid Alamodactylus was a medium-sized pterosaur that lived above the Western Interior Sea during the Late Cretaceous. It is currently considered to be a close relative of animals like Nyctosaurus , another Interior Sea pterosaur whose fossils are found in Kansas. Scientists first studied Alamodactylus from a partial wing skeleton discovered in the Atco Formation of Texas. It was initially thought to be related to Pteranodon but in 2013 it was determined to be a distinct genus was named Alamodactylus byrdi after fossil collector Gary Byrd. Cimoliopterus Temporal Range: 95 million years ago Geographic Range: Texas, the UK Species: C. dunni, C. cuvieri, C. colorhinus Diet: Carnivorous, fish, squid Cimoliopterus was a genus of pterosaur that lived in parts of what are now England and North America during the Cretaceous Period. Its snout was tall and narrow, with only a slight widening at the tip, unlike the broader jaw expansions seen in some related fish-eating pterosaurs. Its crest began farther back on the upper jaw and differed in shape and position from those of closely related genera. Its teeth were also organized in a distinctive way with larger teeth near the front of the jaws and smaller, more widely spaced teeth farther back, most likely an adaptation for snagging fish from the surface of the water. Its fossils were first found in the 19th century but it wasn't formally given its own name until a review published in 2013 concluded that the material represented a distinct genus, leading to the establishment of Cimoliopterus . A specimen described in 2015 widened its range to include parts of Texas in what was at that time the southern part of the Western Interior Sea Nyctosaurus Temporal Range: 85 million years ago Geographic Range: Kansas Species: N. gracilis Diet: Carnivorous, fish, squid Nyctosaurus was a pterosaur whose most famous characteristic was an enormous forked crest that projected upward and backward from the skull. In some individuals, this crest was disproportionately large compared to the rest of the body. Nyctosauru s was also one of only a few pterosaurs to lose all of its smaller clawed fingers except the elongated fourth finger that supported the wing membrane. Because of this reduced hand structure, scientists think that Nyctosaurus was highly specialized for flight and may have spent very little time moving on the ground. Its fossils were found in the 19th century in Kansas. Pteranodon Temporal Range: 86 million years ago - 78 million years ago Geographic Range: Central US, Alabama Species: P. longiceps, P. sternbergi Diet: Carnivorous, small fish, squid Pteranodon is by far the best known type of pterosaur, essentially synonymous with the use of the outdated term “pterodactyl”. It had a long pointed toothless beak, and a large bony crest extending from the back of its skull. Its name, which means “toothless wing,” reflects this lack of teeth. With wingspans that could exceed 6 meters (20 feet), Pteranodon ranked among the largest flying animals of its time and was considered the largest pterosaur genus up until the discovery of larger Azdarchid pterosaurs like Quetzalcoatlus . Its lightweight skeleton, elongated wings, and aerodynamic body made it especially well suited for sustained flight above the waters of the Western Interior Sea. Paleontologists believe it fed mainly on fish, which it likely captured from the ocean surface using its long beak. Currently there are two widely accepted species of Pteranodon ; Pteranodon longiceps, which had a long thin crest, and Pteranodon sternberg i which had a wider roughly diamond-shaped crest. Some workers consider Pteranodon sternberg i to be its own genus, Geosternbergia . When fossils of Pteranodon were found in chalk deposits from Kansas in the 19th century, the paleontologist Othniel Charles Marsh initially placed the remains in another group close to the smaller European genus Pterodactylus , but in 1876 he recognized their unusual toothless jaws and established the genus Pteranodon . Over the following decades many more of their fossils were found. In some parts of Kansas, their fossils are extremely abundant and comparatively easy for fossil hunters to find. (BELOW) A model of a Pteranodon longiceps skull on display at the KU Natural History Museum. Most fossils of these animals found in rocks from western Kansas have been compressed or flattened within the rock surrounding the fossils. (BELOW) The middle bones of the wings of a Pteranodon at the KU Natural History Museum. This is part of a composite skeleton. The three fingers on the left side of the image are a feature seen in most pterosaurs with the exception of Nyctosaurus and its closest relatives. The spur of bone between the radius and the 4th metacarpal is called the pteroid bone. This structure anchors the front-most wing membrane, a feature known as the brachiopatagium. Crocodylomorphs (Crocodylomorpha) Giant Crocs of the Western Interior Sea Crocodylomorphs are a group of archosaurian reptiles which includes modern crocodilians and many of their extinct relatives. Today’s crocodylomorphs are generally recognized by their elongated snouts, powerful jaws equipped with conical teeth, protective bony armor embedded in the skin, and muscular tails that they use when swimming. Although many types of extinct crocodylomorphs lived in rivers, lakes, and coastal environments, others became highly adapted to different habitats and niches, including borrowing, terrestrial locomotion, herbivory and life in marine settings. Fossils found in the layers of rock left behind by the Western Interior Sea preserve the remains of both open ocean specialist crocodylomorphs and animals that preferred to live in near-shore and estuarine habitats. Deinosuchus Temporal Range: 82 million years ago - 73 million years ago Geographic Range: North Carolina, Texas, Montana Species: D. hatcheri, D. rugosus, D. riograndensis, D. schwimmeri Diet: Carnivorous, large prey, dinosaurs, fish, turtles Deinosuchus was one of the largest crocodylomorphs known from the fossil record. Its broad skull, heavily constructed jaws, and thick, crushing teeth were adapted for tackling large prey, possibly even hunting large dinosaurs. Its body was protected by robust bony armor plates known as osteoderms. Deinosuchus had a diet composed of a variety of prey, including fish, turtles, and large terrestrial animals that approached waterways. Its range extended over both sides of the Interior Sea with fossils found in North Carolina, Texas and Wyoming in areas which were once swamplands, river basins and coastal estuaries. These animals seem to have been fairly closely related to today’s crocodilians. It would have looked very similar to today’s alligators but with a large bulb-shaped extension on the tip of its snout which is a feature absent in today’s broad-snouted crocodilians. Terminonaris Temporal Range: 96 million years ago - 91 million years ago Geographic Range: Kansas, Alberta Species: T. browni, T. robusta Diet: Carnivorous, fish, marine reptiles, large prey Terminonaris was a marine crocodylomorph that lived in coastal regions of the Western Interior Seaway during the Late Cretaceous. It had a long, slender snout and narrow jaws which were equipped with thin, interlocking teeth well suited for capturing fish and other small aquatic animals. Terminonaris was a large predator, but its skull shape suggests a feeding strategy different from that of today’s broad-snouted crocodilians that are adapted for crushing larger prey and could have possibly been more similar to the fish-hunting strategies seen in today’s gharials. The first fossils from this animal were described in 1904 and given the name “Teleorhinus ”. Because that name had already been used for another organism, the genus was subsequently renamed Terminonaris. Its fossils have since been found in parts of Alberta and Kansas. Media Gallery Suggested References: Archosauria Adams, Thomas L.; Polcyn, Michael J.; Mateus, Octávio; Winkler, Dale A.; Jacobs, Louis L. (2011). "First occurrence of the long-snouted crocodyliform Terminonaris (Pholidosauridae) from the Woodbine Formation (Cenomanian) of Texas". Journal of Vertebrate Paleontology. 31 (3): 712–716. Bell, A. and Everhart, M.J. (2009). “A new specimen of Parahesperornis(Aves: Hesperornithiformes) from the Smoky Hill Chalk (Early Campanian) of western Kansas”. Kansas Academy of Science, Transactions 112(1/2):7-14. Bennett, S.C. (1992). “Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests”. Journal of Vertebrate Paleontology 12 p. 422-434.\ Bennett, S.C. (2001). “The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology”. Palaeontographica, Abteilung A, 260:1-112. Carpenter, K (2003). "Vertebrate Biostratigraphy of the Smoky Hill Chalk (Niobrara Formation) and the Sharon Springs Member (Pierre Shale)". High-Resolution Approaches in Stratigraphic Paleontology. Topics in Geobiology. 21: 421–437. Carpenter, K., Dilkes, D., & Weishampel, D. B. (1995). “The Dinosaurs of the Niobrara Chalk Formation (Upper Cretaceous, Kansas)”. Journal of Vertebrate Paleontology, 15(2), 275–297. Carpenter, K. and Everhart, M. J. (2007). “Skull of the ankylosaur Niobrarasaurus coleii (Ankylosauria: Nodosauridae) from the Smoky Hill Chalk (Coniacian) of western Kansas”. Kansas Academy of Science, Transactions, 110(1/2): 1-9. Chinsamy, A., L. D. Martin and P. Dodson. (1998). “Bone microstructure of the diving Hesperornis and the volant Ichthyornis from the Niobrara Chalk of western Kansas”. Cretaceous Research 19:225-235. Cole, V. B. (2007). “Field notes regarding the 1930 discovery of the type specimen of Niobrarasaurus coleii, Gove County, Kansas”. Transactions of the Kansas Academy of Science 110(1/2): 132–134. Cossette, Adam P.; Brochu, Christopher A. (2020). "A systematic review of the giant alligatoroid Deinosuchus from the Campanian of North America and its implications for the relationships at the root of Crocodylia". Journal of Vertebrate Paleontology. 40 Cumbaa, S.L. and Tokaryk, T.S. (1999). “Recent discoveries of Cretaceous marine vertebrates on the eastern margins of the Western Interior Seaway”. In: Summary of Investigations 1999, Vol. 1, Saskatchewan Geological Survey, Sask. Energy Mines, Miscellaneous Report 99-4.1, p. 57-63. Everhart, M. J. and K. Ewell. (2006). “Shark-bitten dinosaur (Hadrosauridae) vertebrae from the Niobrara Chalk (Upper Coniacian) of western Kansas”. Kansas Academy of Science, Transactions, 109 (1-2):27-35. Hamm, S. A. and M. J. Everhart. (2001). “Notes on the occurrence of nodosaurs (Ankylosauridae) in the Smoky Hill Chalk (Upper Cretaceous) of western Kansas”. Journal of Vertebrate Paleontology 21(suppl. to 3): 58A. Hone, David W.E.; Witton, Mark P.; Habib, Michael B. (2018). "Evidence for the Cretaceous shark Cretoxyrhina mantelli feeding on the pterosaur Pteranodon from the Niobrara Formation". PeerJ. 6 e6031. Liggett, G. A. 2005. A review of the dinosaurs from Kansas. Kansas Academy of Science. Transactions 108(1/2): 1-14. Lucas, Spencer G.; Sullivan, Robert M. (2006-01-01). Late Cretaceous Vertebrates from the Western Interior: Bulletin 35. New Mexico Museum of Natural History and Science. Witton, Mark P. (2013). “Pterosaurs: Natural History, Evolution, Anatomy”. Princeton University Press. ISBN 0691150613. McIntosh, A. P.; Shimada, K.; Everhart, M. J. (2016). "Late Cretaceous marine vertebrate fauna from the Fairport Chalk Member of the Carlile Shale in southern Ellis County, Kansas, U.S.A." Transactions of the Kansas Academy of Science. Myers, T.S. (2010). “Earliest occurrence of the Pteranodontidae (Archosauria: Pterosauria) in North America: New material from the Austin Group of Texas”. Journal of Paleontology 84(6):1071-1081. Myers, T. S. (2015). "First North American occurrence of the toothed pteranodontoid pterosaur Cimoliopterus". Journal of Vertebrate Paleontology. 35 (6): 1–9 Pêgas, R. V.; Holgado, B.; Leal, M.E.C. (2019). "On Targaryendraco wiedenrothi gen. nov. (Pterodactyloidea, Pteranodontoidea, Lanceodontia) and recognition of a new cosmopolitan lineage of Cretaceous toothed pterodactyloids". Historical Biology. 33 (8): 1–15. Prieto-Márquez, A. (2011). "Revised diagnoses of Hadrosaurus foulkii Leidy, 1858 (the type genus and species of Hadrosauridae Cope, 1869) and Claosaurus agilis Marsh, 1872 (Dinosauria: Ornithopoda) from the Late Cretaceous of North America". Zootaxa. 2765: 61–68. Reynaud, F. (2006). “Hind limb and pelvis proportions of Hesperornis regalis: A comparison with extant diving birds”. Journal of Vertebrate Paleontology 26(3):115A. Shimada, K., and Parris, D.C., (2007). “A long-snouted Late Cretaceous crocodyliform, Terminonaris cf. T. browni, from the Carlile Shale (Turonian) of Kansas”. Transactions of the Kansas Academy of Science 110(1):107-115. Witton, Mark (2010). "Pteranodon and beyond: The history of giant pterosaurs from 1870 onwards". Geological Society, London, Special Publications. 343 (1): 313–323

The Western Interior Sea once spanned from the Gulf of Mexico to the Arctic Ocean and split North America in two during the Late Cretaceous period Timeline Of Prehistoric Life In The Midwest The Geologic Timescale When we look back at the entire history of the Earth, it is often useful to be able to divide the entire 4.56 billion year story of the planet into smaller increments. The geologic timescale divides Earth's history into a series of chronologically-ordered divisions which are themselves defined by major events in Earth's history. It is used by geologists and paleontologists to organize and date different rock layers and the fossils they hold. You may have heard of some of the geochronologic units found on the geologic timescale before; the Cretaceous and Jurassic periods are some well known examples. The boundaries between geochronologic units are defined by divisions between chronostratigraphic units. Chronostratigraphic units represent all of the rocks deposited over the course of a particular time interval. These units are based on the relative ages of different rock deposits. In cases where certain fossils are known to be very common in rocks from a particular chronostratigraphic unit, the appearance or disappearance of these index fossils can be used to define the start and end of a particular unit of time. For instance, the Jurassic system (a chronostratigraphic unit) contains all rocks deposited during the Jurassic period (a geochronologic unit) and the start of the Jurassic is defined by the first appearance in the fossil record of the ammonite Psiloceras spelae tirolicum. By looking at each of the units of time on the geologic timescale, we can get a general sense of what was happening on Earth at a particular time in the history of the planet. For example, rocks from the Campanian stage of the Cretaceous period found in Kansas preserve the remains of marine animals living in warm shallow waters. Similarly, rocks from the early Permian period in the eastern part of the state were formed 215 million years earlier, when that part of the world was covered in coastal rainforests filled with giant amphibians and millipedes. Jump To Section 1. The Cenozoic Era (66 million years ago - Present): After the extinction at the end of the Cretaceous period mammals become some of the largest animals found on Earth. The planet's climate slowly cools until large-scale glaciation covers many parts of the Midwest in ice sheets during the Pleistocene epoch. 3. The Paleozoic Era (538.8 - 252 million years ago): Life diversifies in the world's oceans and begins to move onto land. The first trees, insects, reptiles, amphibians and fish appear during this era. At various times during the Paleozoic the Midwest is covered in shallow seas or in huge rainforests filled with giant scale trees. 2. The Mesozoic Era (252 - 66 million years ago): Reptiles begin to take over new niches in the water, on land and in the skies. The first marine reptiles, pterosaurs, crocodylomorphs and dinosaurs appear during this era. Mammals and flowering plants also get their start during the Mesozoic. The Great Plains are covered in a shallow seaway during the second half of the Cretaceous period. 4. The Early Earth (4.56 billion years ago - 538.8 million years ago): The Earth and Moon are formed and the crust of the planet hardens into solid rock. The first oceans spread across the world and land is fairly rare. Life appears in the fossil record for the first time and by the end of the Proterozoic era, simple animals can be found living in the shallow seas of the Midwest. How To Read The Geologic Timescale The geologic timescale is composed of several different kinds units used to categorize spans of time. The largest units are eons, which usually span across billions of years or hundreds of millions of years. Each eon contains multiple eras, which are units of time lasting hundreds of millions or tens of millions of years. Eras are further broken down into periods, lasting tens of millions of years. Geologic periods are divided into units called epochs and ages which can last anywhere from millions of years to tens of thousands of years. Eons Eons are the largest units of geologic time. The history of the Earth is separated into four eons; the Hadean eon (4.65 billion years ago - 4 billion years ago), the Archaean eon (4 billion years ago - 2.5 billion years ago), the Proterozoic eon (2.5 billion years ago - 538.8 million years ago) and the Phanerozoic eon (538.8 million years ago - present). The Phanerozoic is the eon in which we are currently living. The name "Phanerozoic" means "visible life" since this era begins around the time that complex multicellular life began to proliferate. The entire evolutionary histories of mammals, reptiles, fish, insects, arachnids and land plants fall within the Phanerozoic eon. Eons are divided into smaller units called eras. Within the Phanerozoic eon there are three eras. The first of these is the Paleozoic era (538.8 - 252 million years ago) during which complex animal life diversified and the first vertebrates appeared and spread onto land. The Paleozoic contains six geologic periods; the Cambrian period, the Ordovician period, the Silurian period, the Devonian period, the Carboniferous period and the Permian period. The Paleozoic era was followed by the Mesozoic era (252 - 66 million years ago) which is often called the "age of reptiles". This is the span of time during which dinosaurs, birds, mammals and flowering plants appear in the fossil record. This era is divided into three periods; the Triassic period, the Jurassic period and the Cretaceous period. The Mesozoic era transitions over to the Cenozoic era at the end of the Cretaceous period 66 million years ago when an asteroid impact resulted in a mass extinction event. The Cenozoic era (66 million years ago - present) is the current era of geologic time. This span of time saw mammals move into many of the niches left behind after the extinction of the non-avian dinosaurs. It is divided into three periods; the Paleogene period, the Neogene period and the Quaternary period. The Quaternary period began 2.58 million years ago and is the time period which includes the present day. Eras and Periods Epochs, Ages and Stages Periods can further be divided into smaller units of time called epochs. An epoch usually lasts anywhere from tens of millions of years to tens of thousand of years. The current period of geologic time; the Quaternary period, is divided into the Pleistocene epoch (2.58 million years ago - 11,700 years ago) and the Holocene epoch (11,700 years ago - present). Mesozoic time periods are divided into "early", "middle" and "late" epochs, i.e. the Upper Cretaceous epoch or the Early Jurassic epoch. By putting all of this information together we can say that, for instance, we are currently in the Holocene epoch of the Quaternary period of the Cenozoic era of the Phanerozoic eon! Tyrannosaurus rex , on the other hand, lived in the Late Cretaceous epoch of the Cretaceous period of the Mesozoic era of the Phanerozoic eon. Some time periods and epochs are so long that it becomes useful to further divide them into units called ages. These ages are also often referred to using their chronostratigraphic equivalent unit term "stages". These ages often span a few million years. The Cretaceous period, for instance, is divided into two epochs; the Late Cretaceous and the Early Cretaceous. The Late Cretaceous is composed of six ages/stages; the Maastrichtian, the Campanian, the Santonian, the Coniacian, the Turonian and the Cenomanian. The Early Cretaceous epoch also has six ages/stages; the Albian, the Aptian, the Barremian, the Hauterivian, the Valanginian and the Berriasian. Many simplified representations of the geologic timescale like the one below will show the periods of the Phanerozoic (Cambrian- Quaternary) but will not show the periods of the previous three eons. The 12 phanerozoic periods can also be listed with their 1-2 letter abbreviations. These spans of time also have their own associated colors. Eons don't have universally accepted abbreviations so they are shown here as Had. (Hadean), Arch. (Archaean) and Prot. (Proterozoic). Abbreviations Cambrian period - Ꞓ Ordovician period - O Silurian period - S Devonian period - D Carboniferous period - Ꞓ Permian period - P Triassic period - T Jurassic period - J Cretaceous period - K Paleogene period - Pg Neogene period - Ng Quaternary period - Q The Early Earth 4.56 billion years ago - 538.8 million years ago For the vast majority of Earth's history there were no plants, no animals, no fungi. For billions of years the entire planet was only home to simple single-celled organisms such as archaea. These first living things were closely tied to the presence of liquid water and may have gotten their start near hydrothermal vents or in warm mineral-rich geothermal springs. Plants first appeared as simple algae-like photosynthetic organisms sometime during the Proterozoic eon. It wouldn't be until the very end of the Proterozoic that organisms we might recognize as animals first appeared. The span of time previously known as the "Pre-Cambrian", now divided into the Hadean, Archaean and Proterozoic eons, comprises more than 70 percent of the history of the planet. It includes the earliest days of the Earth when our planet was still a ball of molten rock floating in space, as well as later periods of extreme cold when the planet would have nearly been covered in ice from pole to pole The Hadean eon is the first of four eons which make up the history of the Earth. This first span of around 750 million years saw the planet begin to coalesce from smaller pieces of metal and rock orbiting around the sun. Early on it its history, Earth is thought to have collided with another proto-planet called Theia, which resulted in the formation of the moon. The outer crust of the planet cooled into solid rock during the Hadean eon and the Earth developed its first atmosphere, which was composed of large amounts of methane, water vapor and ammonia. As The Earth cooled, some of this water vapor condensed to form the first oceans. Asteroids and comets rained down on the planet's surface bringing water, gasses, metals and other materials along with them. The end of the Hadean saw a particularly intense series of collisions during a time period called the Late Heavy Bombardment during which asteroid and comet impact became much more common. The first life forms on Earth may have appeared towards the end of the Hadean or during the first half of the next eon, the Archaean. During this eon the Earth was almost completely covered in a deep ocean, with only a few rare islands poking above the surface of the water. Cyanobacteria first appeared during this eon. Some of these ancient organisms are known from ancient fossils, known as stromatolites, which are formed from the cemented and layered remains of some types of microbial mats. The atmosphere was still oxygen-poor and was composed of large amounts of methane gas. The next eon, the Proterozoic, is the longest eon in the history of the Earth. Oxygen became an important component of the atmosphere and the world's oceans during the early part of this eon. A second oxygenation event later in the Proterozoic caused a series of glaciation events which may have covered nearly the entire planet in ice. Life became increasingly complex during the Proterozoic. The first microscopic plants appeared in the oceans during this eon, as did the first eukaryotic single-celled organisms. Some of the first groups of true animals appeared at the very end of the Proterozoic, including ancestors of sponges and jellyfishes. (ABOVE) A scene set during the late Archaean eon showing a cluster of stromatolites in the foreground. The rising levels of oxygen in the atmosphere have turned the sky a pale shade of blue while in the distance a few scattered volcanic islands stand in the middle of a vast global ocean Next Section The Paleozoic Era

Explore the different types of prehistoric sharks who once lived in the Western Interior Sea during the Cretaceous period, including Squalicorax, Cretoxyrhina and Ptychodus Sharks Sharks of the Cretaceous Seas Sharks are a specialized group of cartilaginous fishes that can be distinguished from rays, skates, chimaeras and other related animals by a suite of unique characteristics; namely their torpedo-shaped bodies, multiple visible gill slits, and strong fluke-shaped tails. Sharks are covered with dermal denticles, tiny tooth-like scales that reduce water resistance. They also have advanced senses which let them detect vibrations and electrical signals in the water. Unlike many fishes, sharks do not have swim bladders and instead maintain their buoyancy with the help of large, oil-filled livers. The Western Interior Sea supported a wide variety of shark species, including large macropredatory carnivores, durophagous shell-crushers and benthic ambush hunters. Anatomy External Anatomy The external anatomies of sharks vary widely between different groups but some characteristic features are shared by most sharks. Most types of sharks have five external gill slits on each side of their heads, situated in front of their pectoral fins. They tend to have two dorsal fins, two pectoral fins, two pelvic fins and an anal fin. Their caudal fin is divided into a ventral and a dorsal lobe and is often separated from the rest of the body of the animal by a keel and a small indendation called a precaudal pit. Many types of sharks also have a small opening behind each of their eyes called a spiracle. These spiracles are used to take in water which is then fed over their gills so that the shark can breathe while standing still. These animals also have external openings for their nares and some orders of sharks have distinctive whisker-like barbs used to detect prey. Most sharks have mouths with multiple rows of replacement teeth in reserve behind their main set of functional teeth. (BELOW) General external antatomical features of a a shark, Cardabiodon . Not all of these features are present in every type of shark. Dogfish sharks lack an anal fin, angelsharks have large pectoral fins and flattened bodies. Most sharks have torpedo-shaped bodies which taper off gradually between the dorsal fin and the caudal fin. Skeletal Anatomy The skeletons of sharks are not ossified like those of tetrapods or ray-finned fishes. Instead, most parts of their skeletons are composed of a more flexible material called cartilage. Key structures such as the muscles of the fins, the arches of the gills, the jaws and pectoral arches are supported by cartilaginous rays and arcing structures. The skulls of sharks are formed from a larger set of cartilaginous structures which together form the chondocranium. The cartilages of the jaws are composed of the cartilage of the upper jaws and the Meckel's cartilage of the lower jaws. Along the length of the body of the shark runs the vertebral column, formed of flexible bundles of cartilage which encase the spinal cord. (BELOW) Skeletal anatomy of a shark showing the positions of key cartilaginous structures. In some Cretaceous sharks older individuals have tougher material infusing their skeletons with age. As a result, more complete remains of these animals sometimes make it into the fossil record. Complete remains of Squalicorax , for instance, turn up in Cretaceous marine strata. Teeth and Jaws The jaws of sharks are composed of several cartilaginous structures. The upper jaws form a distinct arc supported by the palatoquadrate cartilages. The lower jaws are formed from the Meckel's cartilage. The cartilages of the jaws are joined along the middle at a point called the symphysis. Different areas across the jaws of sharks support different tooth shapes. (BELOW) The anatomy of the jaws of a shark. The foremost teeth face outwards as a set of functional teeth while a series of replacement tooth rows sit in the rear. As a tooth falls out of the functional row the replacement teeth move up to fill their places. By looking at the particular shape of a shark tooth it is possible to tell where in the shark's mouth it would have originated. The largest teeth are in the anterior and lateral sections of the mouth while very small symphysial teeth are positioned along the symphysis of the Meckel's cartilages. (BELOW) General structure of a shark tooth. The upper part of the shark tooth is composed of the tooth root, positioned at the point where the tooth joins with the jaw cartilages and the gum tissue. The transverse groove seen on the roots of some of these teeth are positioned on the inward-facing (lingual) side of the tooth. (BELOW) A selection of shark tooth types found in deposits from the Western Interior Sea. These teeth came from a wide variety of different types of sharks occupying a range of niches, including shell crushers, fish-eating soft prey specialists and macropredatory animals who fed primarily on large vertebrate prey. Sharks Not all sharks are listed on this page. See the list below for the order in which shark entries are listed Next page This page Order Orectolobiformes Chiloscyllium Cretorectolobus Orectoloboides Plicatoscyllium Order Lamniformes Archaeolamna “Carcharias” Cardabiodon Cretolamna/Cretalamna Cretodus Cretoxyrhina Dallasiella Johnlongia Leptostyrax Odontaspis Paranomotodon Protolamna Pseudocorax Pseudomegachasma Ptychodus Scapanorhynchus Squalicorax Order Carcharininiformes Archaeotriakis Galeorhinus Palaeogaleus Squatigaleus Order Synechodontiformes Paraorthacodus Synechodus Order Squatiniformes Squatina Order Heterodontiformes Heterodontus Order Squaliformes Squalus Order Hexanchiformes Hexanchus Unclear Affinities Aquilolamna Next Page Carpet sharks (Orectolobiformes ) Nurse Sharks, Bamboo Sharks, Wobbegongs Orectolobiform sharks, often referred to as carpet sharks, are a group of sharks which can be recognized by the presence of a set of barbels located near their nostrils, which help them with finding prey on the seafloor, and the particular position of their mouths which are located toward the front of the head. Unlike most types of open-water sharks, orectolobiforms are typically adapted to life near the bottom in near-benthic environments where camouflage plays an important role in avoiding predators and ambushing prey. Living members of this group include nurse sharks, whale sharks, zebra sharks, and wobbegongs. The rocks left behind by the Western Interior Sea preserve the fossil remains of members of the families Ginglymostomatidae and Orectolobidae. Fossils assigned to genera such as Cretorectolobus are fairly rare but their presence serves as a hint that these animals already occupied bottom-dwelling niches and would have fed on small benthic marine animals just as their relatives do to this day. Cantioscyllium Temporal Range: ~123 - 66 million years ago Geographic Range: North America, Europe, western Asia Species: C. decipiens, C. meyeri, C. brachyplicatum, C. hashimiaensis Diet: Ambush predator, benthic invertebrates Cantioscyllium is an extinct genus of Cretaceous nurse sharks. Among Cretaceous carpet sharks it is somewhat notable since it seems to be known from fairly complete fossils of its chondocranium, in addition to the more common fossils of its teeth. Skeletal fossils of Cantioscyllium show that these were small-medium sized sharks with fairly similar proportions to their living relatives. Their teeth are small, triangular, fairly blunt and seem to be well adapted for crushing the shells of benthic invertebrates, such as decapods. It likely hunted near the ocean floor in life, using its sensory barbels to search for food hiding beneath the marine substrate of the ocean floor. Chiloscyllium Temporal Range: 95 million years ago - Present Geographic Range: Worldwide distribution Species: C. broenirnani (extinct) , C. arabicum, C. burmensis, C. caeruleopunctatum, C. griseum, C. hasselti, C. indicum, C. plagiosum, C. punctatum Diet: Carnivorous, small fish, invertebrates Chiloscyllium is a genus of bamboo sharks that is known from fossils found in the Cretaceous but which still has living species found in the world’s oceans today. These animals are adapted for spending their lives near the seafloor. Unlike their wobbegong relatives, bamboo sharks have fairly narrow bodies for carpet sharks. Their dorsal fins are positioned far towards the back of their bodies. Many living genera have skin with splotchy or striped patterns to help keep these animals hidden. Remains of Chiloscyllium from deposits originating in the Western Interior Sea mostly come in the form of fossilized teeth. Their teeth are very small and triangular with large central cusps. Their fossils are found in layers of chalk and shale deposited throughout the Great Plains and eastern North America. (BELOW) A Chiloscyllium tooth. The teeth of these animals are particularly small with a large middle cusp. Original photo taken by Dylan Falkner/Prehistoric Alabama (BELOW) A living example of an extant Chiloscyllium species; C. punctuatum . These animals tend to stay near the seafloor and take shelter in reefs or in the cracks between large rocks. Image by Zul M Rosle, distributed via Wikimedia commons under a CC BY 2.0 license. Cretorectolobus Temporal Range: 129 - 66 million years ago Geographic Range: Central North America, parts of the UK Species: C. olsoni, C. gracilis, C. robustus Diet: Ambush predator, small fish and invertebrates Cretorectolobus was an extinct member of the carpet shark family orectolobidae. These animals had teeth that were relatively narrow and specialized for grasping prey, whereas some other carpet sharks had broader tooth forms adapted to a wider variety of feeding strategies such as cutting or shell-crushing. Although modern wobbegongs are often characterized by elaborate skin flaps and highly developed camouflage styled after clumps of seaweed or kelp, the appearance of Cretorectolobus is known mainly from its teeth which makes it difficult to determine whether it shared all of those adaptations for hiding on the sea floor. Its fossils are found on both sides of the Atlantic in Europe and North America in places which were covered by warm shallow seas during the Late Cretaceous. Orectoloboides Temporal Range: 97 - 94 million years ago Geographic Range: Central North America, parts of Europe Species: O. parvulus, O. multistriatus, O. reyndersi, O. angulatus, O. gijseni Diet: Ambush predator, small fish and invertebrates Orectoloboides was an extinct genus of carpet shark that belonged to the same broad group as modern wobbegongs. Like its living kin, it likely depended on camouflaged patterning to hide from its prey before lunging out in an ambush attack. Its relatively small teeth suggest that it fed on smaller animals rather than the large prey targeted by the more famous large Cretaceous mackerel sharks. Fossils of Orectoloboides from rocks deposited by the Western Interior sea consist primarily of isolated teeth. Plicatoscyllium Temporal Range: 76 - 66 million years ago Geographic Range: Central North America, parts of Europe and western Asia Species: P. derameei, P. gharbii, P. globidens, P. lehneri, P. minutum, P. youssoufiaense Diet: Suction feeder, small fish, molluscs, echinoids Plicatoscyllium is an extinct genus of nurse sharks and a member of the family Ginglymostomatidae, a group which still has many living members to this day. Its remains were originally assigned to the genus Ginglymostoma , the same genus as living nurse sharks, but later studies showed that their dental features were unique enough to justify placing them in a separate genus. The teeth of these sharks had characteristic crown and root shapes with many pairs of lateral cusplets and a broad main cusp. Their teeth are very small, usually less than a centimeter long. This genus also had a widespread fossil distribution and fossil teeth attributed to this genus have been recovered from Late Cretaceous deposits across North America, Europe, North Africa, and the Middle East. It seems to have been mostly confined to the northern hemisphere. Mackerel sharks (Lamniformes ) Mackerel Sharks of the Interior Sea Lamniform sharks, often referred to as mackerel sharks, are a group of fishes which includes today’s great white sharks, mako sharks, threshers, and goblin sharks. This group includes the largest known macropredatory shark species and the members of this order tend to have streamlined bodies, powerful tails, large jaws, and sharp teeth designed for capturing and slicing prey. Many lamniforms also use a reproductive strategy in which developing embryos grow inside the mother and may feed on unfertilized eggs before birth. Lamniform sharks reached the peak of their diversity during the Late Cretaceous with hundreds of species found all across the world and occupying ecological niches all across the ocean food web, from giant macropredators to smaller soft prey specialists. Archaeolamna Temporal Range: 100 - 66 million years ago Geographic Range: Central North America, parts of Europe and Australia Species: A. kopingensis, A. striata, A. haigi Diet: Carnivorous, fish, soft-bodied cephalopods Archaeolamna was a medium-sized genus of shark which is estimated to have measured around 12 feet long. Evidence from its fossil distribution suggests that Archaeolamna was associated with temperate marine environments and some researchers have suggested that it exhibited an antitropical distribution preferring colder habitats similar to the ranges of the modern porbeagle shark. Its teeth have sometimes been found associated with the skeletons of large marine reptiles from the Western Interior Sea. These may have been leftover traces of scavenging behavior from Achaeolamna feeding on carcasses on the seafloor. "Carcharias" Temporal Range: 99 million years ago - Present Geographic Range: Worldwide distribution Extinct Species: C. amonensis, C. tenuiplicatus, C. holmdelenesis Diet: Carnivorous, fish, squid, belemnites Carcharias amonensis was a mid-sized species of sand tiger shark. It had slender pointed teeth which were ideally suited for seizing and holding soft-bodied, fast-moving prey such as fish, squid and belemnites. It seems to have filled the ecological niche of a mid-sized carnivore living in rudist and oyster reef ecosystems. Fossil teeth belonging to Carcharias amonensis have been recovered from numerous rock units in Kansas, South Dakota, and Colorado in areas which were once covered by shallow sunlit seas. The shape of the bodies of Carcharias amonensis are difficult to determine from the fossil record but they were probably similar to living members of the Carcharias genus, with long thick dorsal caudal fin lobes, wide heads and small eyes. Cardabiodon Temporal Range: 95 - 91 million years ago Geographic Range: Worldwide distribution away from the equator Species: C. ricki, C. venator Diet: Carnivorous, fish, smaller sharks, marine reptiles Cardabiodon was a large Cretaceous lamniform shark known from some decent skeletal fossil material which suggests that it was an animal with a deep, heavily built body and a unique dentition that was sufficiently different from other lamniform sharks to place it within its own family, Cardabiodontidae. Its teeth were large, sturdy, and adapted for firmly grasping sizable prey. Its fossils were first found in parts of Australia but it has since been found in environments across the world, including in areas once covered by the Western Interior Sea. It seems to have preferred cooler, temperate marine environments. Fossils have been recovered from regions that were once temperate coastal and offshore seas, and evidence suggests that the genus may have lived in non-tropical environments on either side of the equator, similar to the antitropical distribution of the range of the extant porbeagle shark. (BELOW) A Cardabiodon tooth from the lower middle Turonian, Eagle Ford Formation of Texas. Fossil collected and original image taken by Jared Cooke/ jcookepaleo Cretolamna/Cretalamna Temporal Range: 115 - 46.25 million years ago Geographic Range: Worldwide distribution Species: C. appendiculata, C. lata, C. borealis, C. biauriculata, C. maroccana, C. deschutteri, C. hattini, C. bryanti, C. sarcoporthea Diet: Carnivorous, fish, smaller sharks, marine reptiles Cretalamna/Cretolamna was a generalist lamniform shark which seems to be an early member of the megatoothed sharks. Cretalamna is considered to be an early representative of the evolutionary lineage that eventually gave rise to the giant otodontid sharks, including Otodus megalodon . Its classification within this group is usually based on the wideness of the main cusps of their teeth and their wide tooth roots with shallow root notches. Based on fossils of their skeletal material, it seems as though these animals would have been built similarly to living porbeagle or salmon sharks. They would have had large eyes, fairly deep bodies and pointed slightly recurved dorsal and pectoral fins. Their fossils have been discovered in marine deposits across the globe including those of the Western Interior Sea. Most species likely preyed on fishes and other marine vertebrates, and larger individuals may have been capable of hunting larger marine reptiles. (BELOW) A Cretolamna tooth. The teeth of this genus usually have very large and pointed lateral cusplets. Original photo taken by Dylan Falkner/Prehistoric Alabama (BELOW) A Cretolamna tooth from the Campanian Ozan Formation of Texas. Fossil collected and original image taken by Jared Cooke/ jcookepaleo Cretodus Temporal Range: 100 - 89 million years ago Geographic Range: Central North America, parts of Europe and Africa Species: C. crassidens, C. semiplicatus, C. longiplicatus, C. gigantea, C.houghtonorum Diet: Carnivorous, fish, marine reptiles Cretodus was a large lamniform which is known from some pretty complete fossil skeletons. These animals would have had broad heads, expansive jaws, and heavily built bodies that more closely resembled those of modern tiger sharks than the sleek profile of high-speed predators such as Cretoxyrhina . Evidence from the shapes of its vertebrae and skin denticles tell us that it was a strong but moderately paced swimmer, not necessarily built for quick bursts of speed. They would have been some of the largest carnivores in their habitats capable of hunting large marine vertebrates. Some moderately-sized species grew to be more than 15 feet long, while the largest known individuals may have approached lengths of around 25 feet. This would make Cretodus one of the largest predatory sharks of its time. Its teeth have a very large, wide dominant central cusp flanked by much smaller lateral cusplets. These cusplets were separated from the main cusp but remained connected by a band of enamel. Some of their large main cusps have some slight groove-like banding along their bases. (BELOW) A Cretodus tooth from the early Coniacian of Texas. Fossil collected and original image taken by Jared Cooke, jcookepaleo Cretoxyrhina Temporal Range: 107 - 73 million years ago Geographic Range: Worldwide distribution Species: C. mantelli Diet: Carnivorous, fish, sharks, marine reptiles Cretoxyrhina , also known as the “Ginsu shark,” is probably of the most famous of all Late Cretaceous sharks. It is well known for the fossils of its large, blade-like teeth with thick enamel that were highly effective for piercing, immobilizing, slicing, and dismembering large animals. Its postcranial body shape was comparable to that of modern lamnid sharks and it seems to have been adapted for reaching very high swimming speeds. These animals could grow to be larger than a great white shark, although the proportions of their skulls were rather unique, with large eye sockets and short faces. Cretoxyrhina occupied the role of a top marine predator and likely hunted large fishes, marine reptiles, and other large vertebrates living in the Cretaceous seas. Although the species was initially recognized from isolated teeth found in Europe and eastern North America, later discoveries in formations such as those made in the Smoky Hill Chalk of Kansas yielded exceptionally preserved material, including partial skeletons, vertebrae, jaws, cranial cartilage, and associated tooth sets. As these animals grew older, parts of their cartilaginous skeletons became infused with tougher bone-like material which made their skeletons more likely to fully fossilize. (BELOW) A skeleton of Cretoxyrhina on display at the KU Natural History Museum. The remains of this shark were found in association with the remains of a Xiphactinus fish. See details below. (BELOW) IMAGE A, Preserved chondocranium of Cretoxyrhina showing preserved rows of teeth and the positions of the jaw cartilages. The snout of the animal would be positioned towards the right of the image (BELOW) IMAGE B, Remains of ribs, teeth and jawbones of a Xiphactinus found in association with the Cretoxyrhina skeleton. This Xiphactinus may have been preyed upon by the shark. Round elements are Cretoxyrhina vertebrae. (BELOW) A Cretoxyrhina mantell i tooth from the Late Cretaceous of Kansas, labial view. These teeth have virtually no lateral cusplets. Photo by Mason Hintermeister, N.Pearson via Wikimedia Commons under a CC BY-SA 4.0 license Dallasiella Temporal Range: 95 - 83 million years ago Geographic Range: Central North America, parts of Europe Species: D. willistoni, D. brachyodon Diet: Carnivorous, fish, squid, small marine reptiles Dallasiella was an unusual genus of Cretaceous lamniform shark. Its teeth were generally more lightly built than those of large apex predators such as Cretoxyrhina and lacked the highly serrated cutting adaptations associated with sharks that specialized in attacking large vertebrate prey. At the same time, the teeth of these animals differed from the more generalized dental morphology of animals like Cretalamna . The teeth of Dallasiella have large main cusps which are often thinner and more strongly curved than other types of large macropredatory lamniform genera. It has been considered at various times a close relative of either Cretoxyrhina and Archaeolamna but it is now considered to be a shark of uncertain familial affinity within the Lamniformes. Johnlongia Temporal Range: 110 - 85 million years ago Geographic Range: Central North America Species: J. parvidens, J. allocotodon Diet: Carnivorous, fish, squid, belemnites, invertebrates Johnlongia was a genus of Cretaceous lamniform sharks placed within the same family as sand tiger sharks. It had long, thin narrow teeth with small lateral cusplets and deep grooves running through their tooth roots. These teeth seem to be adapted for catching small soft-bodied prey. Its fossils are fairly uncommon finds in deposits from the Western Interior Sea. These fish-eating animals seem to have been closely related to animals like Psuedomegachasm a, a possible type of filter feeding odontaspid shark. Leptostyrax Temporal Range: 123 - 75 million years ago Geographic Range: North America, Europe, Africa, Asia, Australia Species: L. macrorhiza, L. stychi Diet: Carnivorous, fish, marine reptiles Leptostyrax was a genus of lamniform shark that may have grown to be more than 26 feet long, making Leptostyrax one of the larger predatory sharks of its era. Its teeth have tall, slender central cusps bracketed by smaller lateral cusplets and a strongly divided root, giving them a superficial resemblance to the teeth of modern sand tiger sharks. However the teeth of Leptostyrax were generally larger and more robust than those of many true sand tiger-like sharks from the Cretaceous. These animals seem to be closely related to animals like Cretodus and Protolamna . They had a cosmopolitan distribution and their fossils are found on nearly every continent. Odontaspis Temporal Range: 136 million years ago - Present Geographic Range: Worldwide distribution Extinct Species: O. aculeatus, O. saskatchewanensis, O. sublatata Diet: Carnivorous, fish, squid Odontaspis is a genus of sand tiger sharks which has living members today but is also known from fossils found in Cretaceous deposits. The teeth of animals in this genus are tall, narrow, and sharply pointed with a long, thin main cusp bracketed by between two and four rather small lateral cusplets. These teeth are ideally suited for spearing and retaining slippery prey such as fish and cephalopods. Beyond its dental characteristics, Odontaspis has many of the typical features seen in most types of sand tiger sharks including a long, narrow tail fluke, an elongated conical snout, small eyes and jaws equipped with rows of outward-facing grasping teeth. They tend to be slower moving sharks who live closer to the sea floor than other types of large and more pelagic lamniform sharks. Paranomotodon Temporal Range: 95 - 66 million years ago Geographic Range: Worldwide distribution Species: P. angustidens Diet: Carnivorous, fish, squid Paranomotodon was an early relative of the living thresher shark and is currently considered a member of the family alopiidae. Unlike some of the larger predatory lamniforms of the Cretaceous who had broad, powerful teeth adapted for attacking large prey, Paranomotodon had comparatively slender teeth with narrow, elongated crowns and sharp cutting edges. These teeth usually don't have any prominent lateral cusplets. These animals are not known from very complete fossil material besides their teeth so the shapes of their bodies aren’t particularly well understood. It's unknown if they would have had the same unique caudal fin shape as living thresher sharks, Based on scaling using living threshers, they were probably smaller than their living relatives. In addition to their presence in shallow saltwater environments, some teeth belonging to these animals have been found in deposits left behind by estuarine and river environments. (BELOW) A tooth from a Paranomotodon . Note the lack of lateral cusplets. Original photo taken by Dylan Falkner/Prehistoric Alabama Protolamna Temporal Range: 140 - 70 million years ago Geographic Range: Worldwide distribution Species: P. sokolovi, P. borodini, P. carteri, P. compressidens, P. gigantea, P. roanokeensis Diet: Carnivorous, fish, small sharks, cephalopods, marine reptiles Protolamna was a fairly large early genus of lamniform shark. Its teeth have large root notches but are fairly narrow. Many of their teeth have triangular cusplets which point outwards away from the central cusp. These animals seem to have been some of the earliest large lamniform shark genera to appear in the fossil record, with their oldest fossils dated to the very early Cretaceous period. Fossils of their teeth are found from deposits which date back to a very long stretch of time in the Cretaceous and it seems that they achieved a nearly global distribution. Although its teeth are comparatively small, size estimates based on the scaling of their vertebral fossils suggest that some species in this genus grew to reach lengths of more than 18 feet. They are known from fossils of their teeth, vertebrae, and dermal denticles. Protolamna was likely an active nearshore predator that fed on fishes, small sharks, cephalopods, and crustaceans. (BELOW) A Protolamna tooth from the Early Cenomanian Grayson Formation of Texas. Fossil collected and original image taken by Jared Cooke/ jcookepaleo Pseudocorax Temporal Range: 95 - 66 million years ago Geographic Range: North America, parts of Europe and Africa, western Asia Species: P. affinis, P. heteromorphus, P. laevis, P. granti, P. heteroserratus Diet: Carnivorous, fish, soft-bodied cephalopods Pseudocorax is a genus of mackerel sharks which was once considered to be a very close relative of sharks like Squalicorax but which has since been moved to a separate family. Its fossils are mostly found in parts of Europe and the southeastern US but some finds associated with this genus are also found in areas once covered by the Western Interior Sea. Its teeth appear somewhat similar to those of Squalicorax in that they have a large main cusp which projects backwards, but most Pseudocorax teeth do not have the same extensive degree of tooth serrations as those of Squalicorax. The front facing mesial edge of this main cusp is also less convex in shape in Pseudocorax than it is in Squalicorax. (BELOW) A Pseudocorax tooth. These teeth are outwardly very similar to those of Squalicorax but they lack large serrations on their cutting edges. Teeth are rather small. Original photo taken by Dylan Falkner/Prehistoric Alabama Pseudomegachasma Temporal Range: 100 million years ago Geographic Range: Central North America, parts of Russia Species: P. casei, P. comanchensis Diet: Filter feeder, plankton Pseudomegachasma is a type of odontaspid shark which has been interpreted as a plankton feeder. This makes it the oldest known plankton-feeding shark currently recognized in the fossil record and the only known member of the sand tiger shark lineage to have evolved this lifestyle. Its existence shows that filter feeding evolved independently within several different groups of cartilaginous fishes during the Mesozoic Era. Its teeth had a very unique shape. They were relatively small and would have had relatively low main cusps with reduced lateral cusplets. These teeth were poorly suited for handling large prey. Instead the shape of their teeth would have been best for a feeding strategy that relied on filtering and straining small planktonic organisms from the water. These adaptations seem to be an example of convergent evolution, as they evolved independently from those of other plankton-feeding sharks like basking and megamouth sharks. Pseudomegachasma was a close relative of the fish eating odontaspid Johnlongia . Ptychodus Temporal Range: 105 - 75 million years ago Geographic Range: Worldwide distribution Species: P. mortoni, P. latissimus, P. articulatus, P. rugosus, P. whipplei, P. multistriatus, P. polygyrus, P. oweni, P. mammillaris, P. marginalis Diet: Durophagous, bivalves, ammonites, possibly sea turtles Ptychodus was a specialized genus of durophagous sharks whose teeth were adapted for crushing through hard-shelled prey. Most Cretaceous lamniform sharks had sharp blade-like teeth designed for seizing and/or cutting prey but Ptychodus would have had broad, flattened teeth forming powerful dental batteries that allowed the shark to feed on clams, ammonites, and other heavily armored marine invertebrates. They may have also hunted the sea turtles which would have lived alongside them in the waters of the Cretaceous seas. The surfaces of their teeth have a unique wavy pattern on their chewing surfaces which somewhat resembles the swirls of a fingerprint. Fossils of Ptychodus teeth have been turning up for hundreds of years and early naturalists studying these remains classified them as belonging to ancient giant porcupinefishes rather than sharks. During the nineteenth century Louis Agassiz determined that these were actually the remains of ancient shell-crushing sharks and formally named the genus Ptychodus . Since then numerous fossils, including isolated teeth, jaw fragments, vertebrae, dermal denticles, and associated cartilage remains, have been recovered from Cretaceous rocks worldwide. More recently, well preserved specimens from Mexico have helped paleontologists reconstruct the shark’s body form. These animals would have had broad snouts, large heads and pointed triangular dorsal and pectoral fins. (BELOW) Tooth plate arrangement of a Ptychodus . These large tooth arrangements were positioned along the animal's palate and lower jaws. (BELOW) A Ptychodus tooth. Image A, top view. B and C front and back view of the tooth. The rounded shapes of these teeth and their distinctive patterns of ridges are a hallmark of the teeth of this genus. Original photo by Dylan Falkner/Prehistoric Alabama (BELOW) A Ptychodus marginalis lateral file tooth from the lower Middle Turonian of Texas. Fossil collected and original image taken by Jared Cooke/ jcookepaleo (BELOW) A Ptychodus mammillaris tooth from the Turonian of Texas. Fossil is shown in lingual view (A), labial view (B) side view (C) and from above (D). Fossil collected and original image taken by Jared Cooke/ jcookepaleo (BELOW) A Ptychodus whipplei tooth still partially embedded in matrix from the Coniacian of Texas. Fossil collected and original photo taken by Jared Cooke/ jcookepaleo Scapanorhynchus Temporal Range: ~119 - 66 million years ago Geographic Range: Worldwide distribution Species: S. lewisii, S. texanus, S. rapax, S. raphiodon Diet: Carnivorous, fish, sharks, marine reptiles Scapanorhynchus is an extinct shark that belongs to the same taxonomic family as the modern goblin shark. Much like today’s goblin sharks Scapanorhychus would probably have had an elongated snout used to detect electrical signals coming from their prey, as well as narrow, pointed teeth. These extinct goblin sharks are also often restored with the same type of extendable jaw cartilages seen in their extant relatives. Despite these similarities, Scapanorhynchus would have filled a very different ecological niche than its deep water relatives found in today’s oceans. Modern goblin sharks are animals who hunt for deep water fish and cephalopods in complete darkness. In contrast Scapanorhynchus appears to have lived in shallower sunlit marine environments including continental shelves and inland seas where it occupied the role of an active predator. Maximum size estimates for some Scapanorhynchus species point to some of these animals being longer than the largest great white sharks. In some Late Cretaceous marine deposits Scapanorhynchus teeth are among the most common vertebrate fossils. (BELOW) An upper anterior tooth from a Scapanorhynchus. Original photo by Dylan Falkner/Prehistoric Alabama (BELOW) A lower anterolateral tooth from a Scapanorhynchus. Original photo by Dylan Falkner/Prehistoric Alabama (BELOW) A lateral tooth from a Scapanorhynchus. Original photo by Dylan Falkner/Prehistoric Alabama Squalicorax Temporal Range: 109 - 66 million years ago Geographic Range: Worldwide distribution Species: S. appenduculatus, S. pristodontus, S. falcatus, S. heterodon, S. primaevus, S. curvatus, S. kaupi, S. serratus, S. yangaensis, S. baharijensis Diet: Carnivorous, Pelagic, fish, sharks, marine reptiles Squalicorax is a genus of lamniform sharks whose teeth are broadly similar to those of living tiger sharks, although the tiger shark is part of a completely separate order and the two sharks do not seem to have been particularly closely related to one another. Squalicorax had broad, triangular teeth with serrations along their cutting edges. In contrast, many contemporary lamniform sharks, including Cretoxyrhina, had narrower teeth with smooth edges that were better suited for gripping prey rather than slicing through flesh. The serrated dentition of Squalicorax made it especially good at cutting meat. It may have been both an active predator and opportunistic scavenger. It probably fed on fish, turtles, marine reptiles, and other vertebrates living in Cretaceous seas. The scientific study of Squalicorax began with the discovery of its abundant fossil teeth which are among the most recognizable shark fossils found in Cretaceous rocks. Early paleontologists described several species based on these distinctive teeth and later discoveries revealed that the genus had a wide geographic distribution with their remains found all across the world. Although isolated teeth are by far the most common fossils known from this genus, rare articulated skeletons sometimes preserve remains of the animal’s vertebrae and parts of their skulls, and even occasionally complete skeletons. Their teeth are often found embedded in the bones of marine reptiles, pterosaurs, and dinosaurs which has led to them being considered one of the most abundant and successful scavengers of the Western Interior Sea and earned them the nickname “crow shark”. (BELOW) The teeth of Squalicorax are broad and triangular. The inward-facing cutting edges of their teeth are heavily serrated. Most teeth from this genus do not have a root notch or prominent lateral cusplets. The teeth of some Squalicorax are more spade-shaped and sometimes nearly symmetrical. Below is a Squalicorax yangaensis tooth collected and photographed by Dylan Falkner/ PrehistoricAlabama (BELOW) A Squalicorax baharijensis tooth from the Early Cenomanian Del Rio Formation of Texas. Fossil collected and original image taken by Jared Cooke/ jcookepaleo (BELOW) A set of Squalicorax pristodontus teeth from the Maastrichtian Corsicana Formation of Texas. Photos taken in labial view (A), and lingual view (B). Fossil collected and original image taken by Jared Cooke/ jcookepaleo See the rest of our entries about Cretaceous sharks by continuing to the next page Next Page Media Gallery Suggested References: Sharks Case,G. R.;H. Cappetta. (1997). “A new Selachian Fauna from the Late Maastrichtian of Texas” (Upper Cretaceous/Navarroan; Kemp Formation) . Münchner Geowiss. Abh. (A)(34):131–189 Cook, T.D.; Newbrey, M.G.; Murray, A.M.; Wilson, M.V.H.; Shimada, K.; Takeuchi, G.T.; Stewart, J.D. (2011). "A partial skeleton of the Late Cretaceous lamniform shark, Archaeolamna kopingensis, from the Pierre Shale of western Kansas, U.S.A.". Journal of Vertebrate Paleontology. 31 (1): 8–21 Everhart, M. J. (2004). “Late Cretaceous interaction between predators and prey. Evidence of feeding by two species of shark on a mosasaur”. PalArch, vertebrate palaeontology series 1(1):1-7. Everhart, M.J. (2017). “Oceans of Kansas - A Natural History of the Western Interior Sea”, Second Edition. Indiana University Press, 460 pp. Everhart, M. J. (2005). “Bite marks on an elasmosaur (Sauropterygia; Plesiosauria) paddle from the Niobrara Chalk (Upper Cretaceous) as probable evidence of feeding by the lamniform shark, Cretoxyrhina mantelli”. PalArch, Vertebrate paleontology 2(2): 14-24. Everhart, M. J. and K. Ewell. (2006). “Shark-bitten dinosaur (Hadrosauridae) vertebrae from the Niobrara Chalk (Upper Coniacian) of western Kansas”. Kansas Academy of Science, Transactions, 109 (1-2):27-35. Jambura, P.L.; Stumpf, S.; Kriwet, J. (2021). "Skeletal remains of the oldest known pseudocoracid shark Pseudocorax kindlimanni sp. nov. (Chondrichthyes, Lamniformes) from the Late Cretaceous of Lebanon". Cretaceous Research. 125 Lucas, S. G.; Sullivan, R. M. (2006). “Late Cretaceous Vertebrates from the Western Interior: Bulletin 35.” New Mexico Museum of Natural History and Science. Maisey, J. G., (1996). Discovering Fossil Fishes. Henry Holt and Company, New York. McAllister, J. A. (1985). “Reevaluation of the formation of spiral coprolites” - University Kansas Paleontology Contributions, Paper 114, 12 p. McIntosh, A. P.; Shimada, K.; Everhart, M. J. (2016). "Late Cretaceous marine vertebrate fauna from the Fairport Chalk Member of the Carlile Shale in southern Ellis County, Kansas, U.S.A." Transactions of the Kansas Academy of Science. Schwimmer, D. R., J.D. Stewart, and G. D. Williams. (1997). “Scavenging by sharks of the genus Squalicorax in the late Cretaceous of North America”. PALAIOS, 12:71-83. Shimada, K. (2007). "Skeletal and dental anatomy of lamniform shark, Cretalamna appendiculata from Upper Cretaceous Niobrara Chalk of Kansas". Journal of Vertebrate Paleontology, 27(3):584–602. Shimada, K. (2008). “Ontogenetic parameters and life history strategies of the Late Cretaceous lamniform shark, Cretoxyrhina mantelli, based on vertebral growth increments”. Journal of Vertebrate Paleontology 28(1):21-33. Shimada, K. and Cicimurri, D.J. (2005). “Skeletal anatomy of the Late Cretaceous shark, Squalicorax (Neoselachii: Anacoracidae).” Paläontologische Zeitschrift 79(2): 241-261. Shimada, K and M. J. Everhart. (2003). “Ptychodus mammillaris (Elasmobranchii) and Enchodus cf. E. schumardi (Teleostei) from the Fort Hays Limestone Member of the Niobrara Chalk (Upper Cretaceous) in Ellis County, Kansas”. Kansas Academy of Science, Transactions 106(3-4):171-176. Shimada, K. and M. J. Everhart. (2004). “Shark-bitten Xiphactinus audax (Teleostei: Ichthyodectiformes) from the Niobrara Chalk (Upper Cretaceous) of Kansas”. The Mosasaur 7, p. 35-39. Shimada, K. and D. J. Martin. (1993). “Upper Cretaceous selachians from the basal Greenhorn Limestone in Russell Co., Kansas”. Kansas Academy of Science Abstracts, 12(78). Shimada, K. (1993). Upper Cretaceous selachians from the Fort Hays Limestone Member of the Niobrara Formation in Ellis County, Kansas. Kansas Academy of Science Abstracts, 12(78). Shimada, Kenshu; Ewell, Keith; Everhart, Michael J. (2004). "The First Record of the Lamniform Shark Genus, Johnlongia, from the Niobrara Chalk (Upper Cretaceous), Western Kansas". Transactions of the Kansas Academy of Science. 107 (3/4): 131–135. Shimada, Kenshu; Popov, Evgeny V.; Siversson, Mikael; Welton, Bruce J.; Long, Douglas J. (2015). "A new clade of putative plankton-feeding sharks from the Upper Cretaceous of Russia and the United States". Journal of Vertebrate Paleontology. 35 (5) Shimada, Kenshu; Everhart, M.J. (2019). "A new large Late Cretaceous lamniform shark from North America, with comments on the taxonomy, paleoecology, and evolution of the genus Cretodus". Journal of Vertebrate Paleontology. 39 (4) Siverson, M. and J. Lindgren. (2005). “Late Cretaceous sharks Cretoxyrhina and Cardabiodon from Montana, USA”. Acta Palaeontol. Pol. 50(2) 301-314. Underwood, C.J.; Cumbaa, S.L. (2010). "Chondrichthyans from a Cenomanian (Late Cretaceous) bonebed, Saskatchewan, Canada". Palaeontology. 53 (4): 903–944. Welton, B. J., and R. F. Farish (1993). "The Collector's Guide to Fossil Sharks and Rays from the Cretaceous of Texas." Before Time, Lewisville, Texas, 204 pp. Williamson, T. E., J. I. Kirkland and S. G. Lucas. (1993). “Selachians from the Greenhorn cyclothem ("Middle" Cretaceous: Cenomanian-Turonian), Black Mesa, Arizona, and the paleogeographic distribution of Late Cretaceous selachians”. J. Paleon. 67(3):447-474.

Explore the types of ammonites who lived in the Western Interior Seaway during the Cretaceous period. Ammonoids (continued) List of Ammonoids Not all ammonoids are listed on this page. See the list below for the order in which ammonoid entries are listed Previous page Family Acanthoceratidae Acanthoceras Burroceras Calycoceras Conlinoceras Cunningtoniceras Dunveganoceras Eucalycoceras Mammites Morrowites Neocardioceras Paraconlinoceras Plesiacanthoceras Plesiacanthaceratoides Pseudaspidoceras Spathites Tarrantoceras Watinoceras Family Anisoceratidae Allocrioceras Family Baculitidae Baculites Sciponoceras Family Binneyitidae Borissiakoceras Family Brancoceratidae Mortoniceras Oxytropidoceras Family Coilopoceratidae Coilopoceras Family Collignoniceratidae Collignoniceras Menabites Prionocyclus Texanites Previous Page This page Family Desmoceratidae Moremanoceras Parapuzosia Family Dipoloceratidae Hystoceras Family Engonoceratidae Engonoceras Metengonoceras Family Forbesiceratidae Forbesiceras Family Gaudryceratidae Anagaudryceras Family Hamitidae Stomohamites Hamites Family Municericeratidae Tragodesmoceras Family Nostoceratidae Cirroceras Didymoceras Exiteloceras Eubostrychoceras Family Pachydiscidae Eopachydiscus Pachydiscus Family Placenticeratidae Placenticeras Proplacenticeras Family Scaphitidae Clioscaphites Desmoscaphites Discoscaphites Haresiceras Hoploscaphites Jeletzkytes Scaphites Trachyscaphites Yezoites Family Schloenbachiidae Schloenbachia Family Sphenodiscidae Sphenodiscus Family Turrilitidae Mariella Ostlingoceras Turrilites Family Vascoceratidae Vascoceras Desmoceratidae Temporal Range: Hauterivian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Moremanoceras, Parapuzosia Family of ammonites with smooth shells, sometimes with faint ribs. Narrow cut-like bands running across the shells show up frequently in some species. Shells are round, about as tall as they are wide. Round, oval-shaped in cross section. (ABOVE) The genus Moremanoceras from the Late Cretaceous, Cenomanian stage. Found in New Mexico, Texas. Species: M. elgini, M. costatum, M. straini, M. bravoense (ABOVE) The genus Parapuzosia from the Late Cretaceous, Cenomanian - Campanian stages. Found in Montana. Species: P. americana, P. bradyi, P. seppenradensis Dipoloceratidae Temporal Range: Turonian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Hystoceras Family of ammonites with slightly involute shells, often loosely spiral in shape. Many genera have a series of small bumps and ridges forming in pairs along the margins of the ventral sides of their shells. Some genera have very pronounced spiny tubercles. Oval-shaped in cross-section (ABOVE) The genus Hystoceras from the Late Cretaceous. Found in New Mexico. Species: H. puercoensis Engonoceratidae Temporal Range: Albian stage - Cenomanian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Engonoceras, Metengonoceras Family of ammonites with involute shells, often with very pronounced and well-spaced ribs. Tubercles are present on many sides of the shell depending on the genus. Some shell ribs branch into two forks as they move towards the outside of the shell. Shallow and usually simple sutures. (ABOVE) The genus Engonoceras from the Early Cretaceous, Albian stage. Found in Kansas, Colorado, Texas. Species: E. stolleyi, E. hilli, E. belviderense, E. subjectum (ABOVE) The genus Metengonoceras from the Early and Late Cretaceous, Albian - Cenomanian stages. Found in Texas, Colorado, Iowa. Species: M. bravoense, M. dumbli, M. aspenanum, M. acutum Forbesiceratidae Temporal Range: Albian stage - Cenomanian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Forbesiceras A family of ammonites with involute shells which are usually taller than they are wide. They have fairly complex sutures with leaf-shaped saddles. Tubercles are rare in most genera from this family. Their shells are thin in cross-section. (ABOVE) The genus Forbesiceras from the Late Cretaceous, Cenomanian stage. Found in Texas. Species: F. conlini, F. baylissi, F. obtectum, F. varicostatum Gaudryceratidae Temporal Range: Barremian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Anagaudryceras Family of ammonites with tall, rather evolute shells. Outside of the shell is smooth or with very faint ribs. Usually no prominent ornamentation. The shells are wide and oval-shaped in cross-section. (ABOVE) The genus Anagaudryceras from the Late Cretaceous, Cenomanian stage. Found in Texas. Species: A. involvulum, A. aurarium, A. subtilineatum, A. sacya Hamitidae Temporal Range: Albian stage - Turonian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Hamites, Stomohamites A family of ammonites with loosely coiled or open-spiral shaped shells. No tubercles on the outsides of their shells. Shells are often covered in closely packed narrow ribs. These sides of their shells are round and convex. Wide and oval-shaped in cross-section. (ABOVE) The genus Stomohamites from the Early and Late Cretaceous, Albian - Turonian stages. Found in Colorado, Kansas, New Mexico, Wyoming. Species: S. virgulatus, S . simplex (ABOVE) The genus Hamites from the Late Cretaceous, Cenomanian- Turonian stages. Found in New Mexico, Colorado, South Dakota, Oklahoma, Texas. Species: S. cimmaronensis Muniericeratidae Temporal Range: Turonian stage - Campanian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Tragodesmoceras Family of ammonites with fairly involute shells with shallow, slightly S-shaped ribs. Tubercles and projections are found in some genera along the inner margins of the shells. Some small tubercles or spines are found in some genera on the lateral-ventral parts of their shells. Roughly round in cross-section. (ABOVE) The genus Tragodesmoceras from the Late Cretaceous, Cenomanian - Turonian stages. Found in Kansas, Colorado. Species: T. bassi, T. carlilensis, T. scotti Nostoceratidae Temporal Range: Turonian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Cirroceras, Didymoceras, Exiteloceras A family of heteromorph ammonites. Their shells are not bilaterally symmetrical and their spirals are not mirrored along a single plane. Most genera have shells with a horizontally-aligned spiral on the sections furthest away from the shell opening, others form in a sort of corkscrew. They are often covered in prominent ribs and/or sets of tubercles, usually on the lateral portions of the shells. Some of their shells end in a tapering pointed hook-shaped tip. (ABOVE) The genus Cirroceras from the Late Cretaceous, Campanian stage. Found in Texas. Species: C. reevesi (ABOVE) The genus Didymoceras from the Late Cretaceous, Campanian- Maastrichtian stages. Found in South Dakota, Montana, Wyoming. Species: D. beecheri, D. cheyennense, D. cochleatum, D. nebrascense, D. stevensoni (ABOVE) The genus Exiteloceras from the Late Cretaceous, Campanian stage. Found in South Dakota, Colorado, Wyoming. Species: E. jenneyi (ABOVE) The genus Exiteloceras from the Late Cretaceous, Turonian-Campanian stage. Found in South Dakota, New Mexico, Wyoming. Species: E. perplexum, E. valdelaxum Pachydiscidae Temporal Range: Albian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Pachydiscus, Eopachydiscus Family of ammonites with evolute spiral shells. Shells usually have ribs, some have tubercles along the inner or outer edges of their spirals. Their cross sections vary from rectangular to oval-shaped depending on the genus but their shells are usually fairly wide. (ABOVE) The genus Pachydiscus from the Late Cretaceous, Campanian - Maastrichtian stages. Found in Colorado, New Mexico. Species: P. catarinae, P. bruneti, P. complanatus, P. albuquerquei (ABOVE) The genus Eopachydiscus from the Early Cretaceous, Albian stage. Found in Texas, Oklahoma, New Mexico, Colorado. Species: E. marcianus Placenticeratidae Temporal Range: Albian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Placenticeras, Proplacenticeras A family of ammonites with involute shells, some genera have wavy ribs along their shells. Tubercles are present in some genera, usually on the ventro-lateral parts of the shells or on the inward-facing parts of the spiral. Thin and somewhat oval-shaped in a cross-section. Some genera have a concave area on their ventral surfaces. (ABOVE) The genus Placenticeras from the Late Cretaceous, Cenomanian - Maastrichtian stages. Found in Texas, New Mexico, New Jersey, Alabama, Wyoming, Delaware South Dakota. Species: P. adkinsi, P. intercalare, P. meeki, P. placenta, P. planum, P. whitfieldi (ABOVE) The genus Proplacenticeras from the Late Cretaceous, Turonian - Campanian stages. Found in Kansas, New Mexico, Texas. Species: P. pseudoplacenta Scaphitidae Temporal Range: Albian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Clioscaphites, Desmoscaphites, Discoscaphites, Haresiceras, Hoploscaphites, Jelekytes, Scaphites, Trachyscaphites A large family of ammonites with loosely coiled shells. Ribs are present in many genera. The areas on some shells just above their openings becomes wide enough to encase other parts of the coiled spirals on their shells, similar to what is seen in more typical involute ammonite shells. Tubercles or spines are present in the shells of some genera. Unlike in many genera, the largest tubercles on the shells of scaphitid ammonites are not always the ones closest to the shell’s opening. Shells are round in a cross-section. (ABOVE) The genus Clioscaphites from the Late Cretaceous, Coniacian to Santonian stages. Found in Texas, Kansas, South Dakota, Nebraska, Wyoming, New Mexico, Colorado, Montana. Species: C. choteauensis, C. montanensis, C. vermiformis (ABOVE) The genus Desmoscaphites from the Late Cretaceous, Santonian to Campanian stages. Found in New Mexico, Colorado, Kansas. Species: D. bassleri, D. erdmanni (ABOVE) The genus Discoscaphites from the Late Cretaceous, Campanian to Maastrichtian stages. Found in Texas New Mexico, Kansas, Wyoming, South Dakota, Alabama, Mississippi. Species: D. abyssinus, D. conradi, D. gulosus, D. nebrascensis, D. rossi (ABOVE) The genus Haresiceras from the Late Cretaceous. Found in Wyoming, Montana. Species: C. casperi, C. hiltensis, C. woolgari, H. placentiforme (ABOVE) The genus Hoploscaphites from the Late Cretaceous, Campanian to Maastrichtian stages. Found in Texas, Wyoming, Kansas, South Dakota, North Dakota. Species: H. birkelundi, H. brevis, H. cheyennensis, H. comprimus, H. dorfi, H. gilberti, H. melloi, H. nebrascensis, H. nicolleti, H. nodosus, H. plenus, H. spedeni (ABOVE) The genus Jeletzkytes from the Late Cretaceous, Campanian to Maastrichtian stages. Found in Colorado, Wyoming, South Dakota, Nebraska, North Dakota. Species: J. dorfi, J. nebrascensis, J. spedeni (ABOVE) The genus Scaphites from the Late Cretaceous, Turonian- Campanian stages. Found in Texas, Kansas, South Dakota, Nebraska, Wyoming, New Mexico, Colorado. Species: S. carlilensis, S. ferronensis, S. hippocrepis, S. inflexus, S. kansiensis, S. leei, S. mariasensis. S. mitchellensis, S. patulus, S. pygmaeus, S. venticosus, S. warreni, S. whitfieldi (ABOVE) The genus Trachyscaphites from the Late Cretaceous, Campanian stage. Found in Texas. Species: T. densicostatus (ABOVE) The genus Trachyscaphites from the Late Cretaceous, Coniacian - Santonian stages. Found in Texas, Arizona, South Dakota, Montana, California. Species: Y. subevolutus, Y. puerculus Schloenbachiidae Temporal Range: Cenomanian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Schloenbachia A family of ammonites whose members have varying spiral shapes. Includes both evolute and subinvolute forms. Ribbing is present in most genera, some types also have low tubercles projecting outwards from their ribs. Oval-shaped in cross-section. (ABOVE) The genus Schloenbachia the Late Cretaceous, Cenomanian stage. Found in Texas. Species: S. trinodosa Sphenodiscidae Temporal Range: Coniacian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Sphenodiscus A family of ammonites which usually have smooth shells or shells with very low tubercles. No spines present in these genera. Shells are involute and broadly similar to those seen in other involute groups like the coliopoceratids. Thin shells in cross section are usually rounded or teardrop shaped with a pointed tapering edge on the ventral side. (ABOVE) The genus Sphenodiscus from the Late Cretaceous. Found in Wyoming, Texas, Kansas, Colorado, South Dakota, Wyoming, . Species: S. beecheri, S. dumbi, S. lenticularis Turrilitidae Temporal Range: Turonian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Cirroceras, Didymoceras, Exiteloceras Ammonites with helix-shaped spiral shells. Many of them often have a pointed tip, usually have ribs along the outsides of the shells. Lateral tubercles or spines are present on the sides of the shells of many genera. Most turrilitids have tightly coiled spiral helixes but a few genera have looser coils with most space in between different elements of their spirals. Smaller turrilitids can sometimes be confused with certain gastropod shells. Round, oval-shaped in a cross-section. (ABOVE) The genus Mariella from the Late Cretaceous, Albian–Cenomanian stages. Found in California, Texas. Species: M. cenomanensis, M. asper, M. bicarinata, M. davidense (ABOVE) The genus Ostlingoceras from the Early and Late Cretaceous, Albian-Cenomanian stage. Found in Texas. Species: O. brandi (ABOVE) The genus Exiteloceras from the Late Cretaceous, Cenomanian–Turonian stages. Found in Colorado, Texas, New Mexico. Species: T. acutus, T. brazoensis, T. dearingi Vascoceratidae Temporal Range: Turonian stage - Maastrichtian stage Diet: Active predator, fish, invertebrates Genera in the Western Interior Sea: Vascoceras Shells are highly variable. Some are evolute and others are fairly strongly involute. Shells can be smooth or wavy. The members of this family have relatively few ribs or tubercles. (ABOVE) The genus Vascoceras from the Late Cretaceous, Cenomanian - Turonian stages. See the rest of our entries about Cretaceous ammonoids by returning to the previous page Previous Page Suggested References: Ammonoids Brinster, K. F. (1970). “Molluscan Paleontology of the Pierre Shale (Upper Cretaceous), Bowman County, North Dakota (MS).” University of North Dakota. Chirat, R., Goriely, A. & Moulton, D., E. (2021) “The physical basis of mollusk shell chiral coiling” in Proceedings of the National Academy of Sciences of the United States of America - Vol. 118, No 48 - National Academy of Sciences Clark, D., L. (1965) “Heteromorph Ammonoids from the Albian and the Cenomanian of Texas and Adjacent Areas” in Memoirs of Geological Society of America: 95 - The Geological Society of America, Inc. Digital Atlas of Ancient Life. “Ammonoidea”. Cretaceous Atlas of Ancient Life | Ammonoidea. https://www.cretaceousatlas.org/orders/ammonoidea/ Everhart, M.J. (2017). “Oceans of Kansas - A Natural History of the Western Interior Sea”, Second Edition. Indiana University Press, 460 pp. Furnish, W. M., Zuren, Z., & Glenister, B. F. (2009). Part L, Mollusca 4 (Revised), vol. 4, Complete Volume. Treatise on Invertebrate Paleontology. Hoffmann, René; Slattery, Joshua S.; Kruta, Isabelle; Linzmeier, Benjamin J.; Lemanis, Robert E.; Mironenko, Aleksandr; Goolaerts, Stijn; De Baets, Kenneth; Peterman, David J.; Klug, Christian (2021). "Recent advances in heteromorph ammonoid palaeobiology". Biological Reviews. 96 (2): 576–610. Ifrim, C. & Stinnesbeck, W. (2010) “Migration pathways of the late Campanian and Maastrichtian shallow facies ammonite Sphenodiscus in North America” Palaeo (Palaeogeography, Palaeoclimatology, Palaeoecology): 292 Inoue, S., Kondo, S. (2016). “Suture pattern formation in ammonites and the unknown rear mantle structure”. Sci Rep 6, 33689. Kauffman, E.G. (2004). “Mosasaur predation on Upper Cretaceous nautiloids and ammonites from the United States Pacific Coast.” Palaios 19(1):96-100. Kennedy, W.J., Landman, N.H., Cobban, W.A. and Scott, G.R. (2000). “Late Campanian (Cretaceous) heteromorph ammonites from the Western Interior of the United States”. Bulletin of the American Museum of Natural History 251, 88 pp Klug, C., Schweigert, G., Lauer, R. et al. (2025) “Reproductive biology and anatomy of ammonites”. Sci Rep 15, 39621. Kruta, I.; Landman, N.; Rouget, I.; Cecca, F.; Tafforeau, P. (2011). "The Role of Ammonites in the Mesozoic Marine Food Web Revealed by Jaw Preservation". Science. 331 (6013): 70–72. Kulicki, C., Tanabe, K. and Landman, N.H. (2007). Primary structure of the connecting ring of ammonoids and its preservation. Acta Palaeontologica Polonica 52(4):823-827. Musick, Glenn (2008). "Utah Ammolite". Rock & Gem. Vol. 38, no. 8. pp. 34–38. Neal L. Larson; Steven D. Jorgensen; Robert A. Farrar & Peter L. Larson (1997).” Ammonites and the Other Cephalopods of the Pierre Seaway.” Geoscience Press, Inc. p. 44 Ward, P., D., Haggart, J., W., Mitchell, R., Kirschvink, J., L. & Tobin, T. (2012) “Integration of macrofossil biostratigraphy and magnetostratigraphy for the Pacific Coast Upper Cretaceous (Campanian-Maastrichtian) of North America and implications for correlation with the Western Interior and Tethys.” Geological Society of America Bulletin - v. 124, no 5/6 - The Geological Society of America Westermann, G. E. G. (1996). “Ammonoid life and habitat. In N. H. Landman, K. Tanabe, and R. A. Davis (editors), Ammonoid Paleobiology, pp. 607–707. New York: Plenum Press. Westermann, Gerd E. G. (1996), "Ammonoid Life and Habitat", in Landman, Neil H.; Tanabe, Kazushige; Davis, Richard Arnold (eds.), Ammonoid Paleobiology, Topics in Geobiology, vol. 13, Boston, MA: Springer US, pp. 607–707 Wright, C. W., (1996). Ammonoidea, in Kaesler, R. L., ed., Treatise on Invertebrate Paleontology, Part L, Mollusca 4, Volume 4. The University of Kansas and Geological Society of America. 362 pp.

Explore the different types of crinoids, sea urchins, brittle stars and starfishes who lived in the Western Interior Sea during the Cretaceous period Echinoderms Starfishes, Sea Urchins and Brittle Stars Echinodermata is a group of marine invertebrates which includes animals like sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, and feather stars. The name “echinoderm” means “spiny skin,” which refers to rough surfaces or spines commonly present on their bodies. Adult echinoderms usually have bodies organized radially with five symmetrical sections arranged around a central point, while their larvae are bilaterally symmetrical. Echinoderms have a skeleton which is built from calcium carbonate structures known as ossicles. They also have an internal system which pumps water through their bodies in order to fill small fluid-filled canals and, in some groups, mobile tube feet. Changes in fluid pressure can make these tube feet stretch out, working together to produce a sort of walking motion. Some echinoderms are fully mobile while others attach themselves to a hard surface or to the loose substrate of the ocean floor. Echinoderm fossils, particularly those of crinoids, are common in deposits from the Paleozoic era but turn up less often in deposits from the Western Interior Sea. Most extant groups of echinoderms had already appeared on the scene by the Late Cretaceous and the most common echinoderm group known from these rock layers are the echinoids, or sea urchins. Echinoderms (Browse by class) Sea Urchins (Class Echinoidea) Codiopsis Cottaldia Goniopygus Cassidulus Echinobrissus Nucleolites Globator Tetragramma Crassiholaster Holaster Anorthopygus Holectypus Gauthiera Phymosoma Goniophorus Salenia Hemiaster Sea Urchins (continued) Heteraster Holanthus Mecaster Micraster Sea Lilies (Class Crinoidea) Dunnicrinus Lakotacrinus Uintacrinus Starfishes (Class Asteroidea) Astrocratis Betelgeusia Coulonia Brittle Stars (Class Ophiuroidea) Brezinacantha Sea Lilies (Crinoidea) Temporal Range: ~480 million years ago - Present Diet: Filter feeders: plankton Genera in the Western Interior Sea: Lakotacrinus, Uintacrinus, Dunnicrinus Crinoids are marine echinoderms structured with a cup-shaped central body, known as the calyx, surrounded by flexible arms bearing many smaller filament-like branches called pinnules. These feather-like structures trap plankton and other suspended food particles before moving them through feeding grooves toward their mouths. Sea lilies are anchored to the ocean floor by a structure called a column. Some types of crinoids, like the extinct Cretaceous genus Uintacrinus or the living feather stars, are free-swimming and are not connected to the seafloor. (ABOVE) Crinoid genera of the Western Interior sea: (A) Lakotacrinus, (B) Uintacrinus, (C) Dunnicrinus (ABOVE) Detail of a slab containing many fossils of Uintacrinus on display at the KU Natural History Museum. Two crinoids have been shaded in order to show their constituent elements Starfishes (Asteroidea) Temporal Range: ~450 million years ago - Present Diet: Active predator, small fish, invertebrates Genera in the Western Interior Sea: Coulonia, Astrocratis, Betelgeusia Starfishes are a type of benthic echinoderm whose bodies are structured as a central disc surrounded by five or more arms. Rows of tube feet line the underside of the body of the starfish and can move the body of the animal by changing the pressure of the seawater passing through an attached vascular system. These tube-feet help the starfish travel, grip surfaces, detect its surroundings, and handle food. Most sea stars hunt invertebrates living on the ocean floor. Some species digest prey by extending their stomach outside their bodies. They also have an internal calcium-based skeleton and can usually regrow injured or missing arms. (ABOVE) Starfish genera found in the Western Interior Sea: (A) Coulonia, (B) Astrocratis, (C) Betelgeusia Brittle Stars (Ophiuroidea ) Temporal Range: ~488 million years ago - Present Diet: Scavengers, carrion, organic detritus Genera in the Western Interior Sea: Brezinacantha Brittle stars, or Ophiuroids, are echinoderms who have five narrow, highly flexible arms extending from a distinct central disc. By twisting and sweeping these segmented arms, they can travel rapidly across the ocean floor. Their tube feet do not have suckers and are mostly used to detect the animal’s surroundings and to gather food. Brittle stars feed on plankton and any type of organic detritus they find on the seafloor. They have longer and more flexible arms than sea stars. (ABOVE) The genus Brezinacantha known from deposits found in the Western Interior Sea. (ABOVE) A collection of Ophiura brittle star fossils found in the early Cenomanian Grayson Formation of Texas, fossils collected and image taken by Jared Cooke/ jcookepaleo (ABOVE) A version of the photo of the brittle star deathbed with the fossils outlined in red. Fossils collected and image taken by Jared Cooke/ jcookepaleo Sea Urchins (echinoids ) Temporal Range: ~465 million years ago - Present Diet: Algae, small slow-moving or stationary invertebrates Order in the Western Interior Sea: Arbacioida, Cassiduloida, Echinoneoida, Euechinoida, Holasteroida, Holectypoida, Phymosomatoida, Salenioida, Spatangoida Sea urchins are marine members of the echinoderm class Echinoidea. Their rounded bodies are protected by a hard internal shell known as a test, which is built from a series of fused calcium carbonate plates. This structure is covered with spines which help to defend the animal and support its movement. The sea urchin’s tube feet can move in and out of small pores in the test to allow the animal to move slowly over the seafloor. The mouth of the sea urchin is found on the lower side of the body and holds a special organ called an Aristotle’s lantern which is used to scrape food off of rocks. Most of the fossils of sea urchins known from areas which were once covered by the Western Interior Sea are fossils of the tests of these ancient echinoids. (ABOVE) Cretaceous echinoids of the order Arbacoida: (A) Codiopsis, (B) Cottaldia, (C) Goniopygus (ABOVE) Cretaceous echinoids of the order Cassiduloida: (A) Cassidulus, (B) Echinobrissus, (C) Nucleolites (ABOVE) The genus Globator, an echinoid from the early and Late Cretaceous of Texas and New Mexico (ABOVE) The genus Tetragramma from the Late Cretaceous of Texas (ABOVE) Cretaceous echinoids of the order Holasteroida: (A) Holaster, (B) Crassiholaster (ABOVE) Cretaceous echinoids of the order Holectypoida: (A) Anorthopygus, (B) Holectypus (ABOVE) Cretaceous echinoids of the order Phymosomatoida: (A) Gauthiera, (B) Phymosoma (ABOVE) Cretaceous echinoids of the order Salenioida: (A) Goniophorus, (B) Salenia (ABOVE) Cretaceous echinoids of the order Spatangoida: (A) Heteraster, (B) Micraster, (C) Mecaster, (D) Hemiaster, (E) Holanthus Gallery: Sea Urchin Fossils Suggested References: Echinoderms Everhart, M. J. "Notes on Uintacrinus socialis Grinnell" https://www.oceansofkansas.com/Uintacrinus.html Williston, S. W. (1894). “Notes on Uintacrinus socialis Grinnell”. Kansas University Quarterly, 3(1):19-21 (includes note by B. H. Hill). Everhart, M.J. (2017). “Oceans of Kansas - A Natural History of the Western Interior Sea, Second Edition”. Indiana University Press, 460 pp. Voultsiadou, Eleni; Chintiroglou, Chariton (2008). "Aristotle's lantern in echinoderms: an ancient riddle" (PDF). Cahiers de Biologie Marine. 49 (3). Station Biologique de Roscoff: 299–302. Aaron W. Hunter, Neal L. Larson, Neil H. Landman, Tatsuo Oji; Lakotacrinus brezinai n. gen. n. sp., a new stalked crinoid from cold methane seeps in the Upper Cretaceous (Campanian) Pierre Shale, South Dakota, United States. Journal of Paleontology 2016;; 90 (3): 506–524.

Over a dozen species of Midwestern animals have become extinct over the last 250 years, including several bird, fish and insect species. Visit our virtual gallery to see illustrations of these lost animals Gallery Of Recent Extinctions Midwestern animals who have disappeared in the last 250 years Over the last two and a half centuries, over a dozen species once found in the Midwestern United States have become extinct. Some of these animals, such as the passenger pigeon, were once so common that they would have been a common fixture on the landscape for generations of people living in this area. Other species were confined to very small ranges and occupied ecological niches which became impossible to hold once humans began to impact the land or water around them. Although ecological factors such as droughts undoubtedly had an impact on the populations of some of these animals, the primary causes of all these extinctions were generated by human activity, including overhunting or overfishing, logging, intentional culls of pests, introduction of non-native competitor species or pollution. Click on the animals to learn more

An illustrated field guide to the extinct megafauna once found in the Midwest during the Pleistocene epoch including mammoths, mastodons, sabertooth cats, camels and ancient horses Guide To The Megafauna Of The Pleistocene Ice age giants in the Midwest The Pleistocene epoch began 2.58 million years ago and ended at the start of the Holocene epoch 11,700 years ago. This stretch of time saw the Midwest play host to many different types of giant ancient land mammals and reptiles, including members of groups which are entirely absent from the North American continent today. Relatives of today's elephants, including mammoths and mastodons, made their homes in the open plains and pine forests, while giant ground sloths browsed on woody vegetation. Parts of the southern plains in Oklahoma and Texas were even home to huge armadillos which could grow to be the size of a small car! Whether due to a changing climate or the arrival of humans, many of these ancient animals disappeared towards the end of the Pleistocene epoch, with most of the largest land mammals having vanished by around 10,000 years ago. Browse animals by taxonomic order/family Or scroll to the bottom of the page to browse by genus Extinct Pleistocene Mammals Elephant relatives (Proboscidea) Mastodons, Mammoths, Gomphotheres Explore Cats and Dogs (Carnivora) Pantherines, Saber-Toothed Cats, Wolves Explore Odd-Toed Ungulates (Perissodactyla) Horses, Tapirs Explore Even-Toed Ungulates (Artiodactyla) Deer, Bison, Camels, Peccaries Explore Sloths and Armadillos (Xenarthra) Giant Ground Sloths, Glyptodonts Explore Giant Beaver Explore Rodents (Rodentia) Extinct Pleistocene Reptiles Tortoises (Testudinidae) Western Giant Tortoise Explore The Pleistocene Landscape Glaciers, tundras and pine forests covered the corn belt The midwest as it was inhabited by the megafauna of the Pleistocene was very different from the land we known today. 700,000 years ago glaciers reached as far south as Kansas City and the area that would one day become the Great Lakes was covered by thousands of feet of ice. Explore the Pleistocene Landscape Browse all Pleistocene taxa Carnivorans Bears (Family Ursidae) Arctodus pristinus Arctodus simus Cats (Family Felidae) Homotherium Miracinonyx American Lion Giant Jaguar Smilodon Dogs and Wolves (Family Canidae) Aenocyon armbrusteri Dire wolf Canis edwardii Proboscidea Cuvieronius Mammuthus columbi Mammuthus primigenius Mammut americanum Stegomastodon Perissodactyla Horses (Family Equidae) Equus scotti Equus simplicidens Haringtonhippus Nannippus Tapirs (Family Tapiridae) Tapirus veroensis Artiodactyla Peccaries (Family Tayassuidae) Mylohyus Platygonus Deer (Family Cervidae) Bretzia Cervalces Camels (Family Camelidae) Camelops Hemiauchenia Palaeolama Titanotylopus Bison, Muskoxen (Family Bovidae) Bison antiquus Bison latifrons Bison occidentalis Bootherium Euceratherium Pronghorns (Family Antilocapridae) Capromeryx Stockoceros Tetrameryx Xenarthrans Sloths (Suborder Folivora) Megalonyx Nothrotheriops Paramylodon Armadillos (Order Cingulata) Dasypus bellus Glyptotherium Holmesina Rodents Castoroides Tortoises Hesperotestudo