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The Midwest was once home to giant tortoises during the Pleistocene epoch. These animals, like the genus Hesperotestudo, had shells which could grow to be over four feet across Tortoises and Turtles Giant Pleistocene Tortoises During the Pleistocene epoch, the Midwest was home to a diverse assemblage of turtles, including both species that survive today and several extinct forms. Freshwater turtles such as pond turtles, snapping turtles, and softshell turtles inhabited rivers, lakes, and wetlands, while terrestrial box turtles had become specialized for life outside the water as specialist burrowers. Among the most impressive turtles found in this region were the giant tortoises of the genus Hesperotestudo , which lived across parts of the southern and central United States and could reach shell lengths exceeding one meter. These large herbivores were among the last giant tortoises to inhabit mainland North America. Western giant tortoise Hesperotestudo sp. Temporal Range: 20 million years ago to approximately 10,000 years ago Geographic Range: Found across southern North America and Central America Species: H. crassiscutata, H. osborniana, H. turgida, H. ducateli , H. orthopygia Diet: Herbivorous, grasses, leaves, fruits, some invertebrates Hesperotestudo was a giant land tortoise that lived in North America during the Pleistocene epoch and was among the largest turtles ever to inhabit the continent. Fossils of several species have been found across the southern and central parts of the US, as well as parts of Central America, where these reptiles occupied warm grasslands, woodlands, and scrub environments. Some North American species grew to shell lengths of more than 3 feet, while others from Central America grew to be nearly 5 feet long, making them much larger than our living types of North American tortoises. The shell of Hesperotestudo was heavily built and provided protection from large Ice Age predators. It likely fed on grasses, leaves, fruits, and other vegetation available in its environment. It seems to have been able to live in colder environments than many giant tortoises can withstand today. (BELOW) A labeled diagram of the skeletal anatomy of a tortoise. In this drawing the shell is presented in cross-section in order to reveal the underlying skeletal features. The vertebrae of the animal's back are fused to the tortoise's shell (BELOW) A labeled diagram of the arrangement of the outer scutes covering the shell of a tortoise. The carapace consists of the bones and scutes found on the dorsal side of the tortoise while the plastron covers the lower part of the body Media Gallery Suggested References: Tortoises Biewer, Jacob; Sankey, Julia; Hutchison, Howard; Garber, Dennis (2016). "A fossil giant tortoise from the Mehrten Formation of Northern California". PaleoBios. 33. doi:10.5070/p9331030312. ISSN 2373-8189. Dunbar, James S.; Webb, S. David (1996). "17. Bone and Ivory Tools from Submerged Paleoindian Sites in Florida". In Anderson, David G.; Sassaman, Kenneth E. (eds.). The Paleoindian and Early Archaic Southeast. University Alabama Press. pp. 331–353. Moll, Don; Brown, Lauren E. (2017). "Reinterpretation of the Climatic Adaptation of Giant Fossil Tortoises in North America". Herpetological Journal. 27 (3): 276–286. Vlachos, Evangelos (2018-04-17). "A Review of the Fossil Record of North American Turtles of the Clade Pan-Testudinoidea". Bulletin of the Peabody Museum of Natural History. 59 (1): 3.

Learn about how we make the illustrations for this website through a step by step guide to the process used by illustrator Corbin Rainbolt to produce a piece of paleoart Our Artistic Process Over the course of the last five years we have produced over 800 drawings for this project, ranging from wide landscape panoramas to simpler drawings of individual extinct animals. Although the subject matter for these drawings can change a lot from illustration to illustration, the process used to draw these animals and landscapes usually follows a similar workflow. In this section I've tried to write down a general summary of the steps needed to make the types of drawings used to show the appearances of individual taxa on this website. (ABOVE) A drawing of a young ceratopsian who has found the decomposing skeleton of an Albertosaurus in what will one day become the Horseshoe Canyon Formation in Alberta, Artwork by Corbin Rainbolt The software we use to make our artwork is all available to download for free online. All of out drawings are made using G.I.M.P. version 2.10.34. This drawing and image editing software is fairly similar to other programs such as Adobe CC products, or Krita, ProCreate etc. It's a good alternative to paid programs and it still includes a lot of the main features that you may be used to using. Visit the G.I.M.P. website GIMP.org How to draw a Deinonychus by Corbin Rainbolt Step 1 The first step of the drawing process is making a basic sketch of an animal in order to get an idea of how I want the drawing to be posed and to make sure I have enough room for the entire animal on my page. I usually do this on its own separate layer and keep the sketch pretty loose since I'll be making a lot more edits to the lines of the drawing before I start to add colors. Step 2 Once I have a good idea of how I want my drawing to be posed I go ahead and make a more refined sketch on top of the layer from the first step of this process. I try and mark out some of the basic anatomical details with directional marks while I plot out the placement of the animal's eyes, nails, teeth, etc. Step 3 One more layer of detail gets added to the lines of the drawing at this stage. This time I try and get as much detail on to the page as possible at this point in order to help guide the workflow of the drawing in future steps. This last line art stage is usually done on a transparent layer. Step 4 Keeping only the detailed line art layer from the last step, I go ahead and mark out the contours of the drawing using a flat color. I usually use light gray to mark out the general shape of the animal. Step 5 I add basic shadows to the drawing by painting them in black on a low-transparency layer. I like to keep the shapes of the shadows on their own layer so that I can use them later as an overlay once I start adding more details/colors. Step 5 Before I start adding basic colors I add a layer for my highlights and mark them out in white. The highlights layer needs to be underneath the shadow layer from step 4. Step 6 The first round of colors I add to the drawing tend to be fairly basic. I don't worry too much about getting the shading just right at this point, its more about figuring out the layout of the color patterns for the skin/fur/feathers. Step 7 On a separate layer above the rest of the drawing I like to make a collage of different types of textures for my illustration. These textures are taken from photos. I often go to the zoo or the aquarium to take a lot of these types of reference photos so that I have a decent amount of images I can use for these collages. Once this step is complete I will then make this collage layer less opaque and begin to work these textures into the drawing itself. Step 8 When the textures from the collage from step 7 are brought into the rest of the illustration it becomes time to start refining the bright spots and shadows. In previous steps the lines between shaded areas and unshaded areas were very abrupt so most of this step involves blending the darker shadows into the rest of the animal's form. Step 9 Once all the coloring and shading work is complete I like to go back over the drawing and make a hatched pattern using a simple circle brush. I use lots of tiny parallel directional lines in order to give more volume to the animal. The hatched lines will ideally match with the contours of the animal and the directions of these lines can tell a viewer a lot about the shape and/or texture of a particular object in the drawing. Final Adjustments The last step in the process is just a matter of going over the drawing and making final adjustments to the colors in the scene or the anatomy of a particular animal. In the case of this drawing of a Deinonychus, I reduced the size of the arms and lengthened the tail using the "warp transform" tool.

Learn more about Prehistoric life by visiting these other websites. Additional links to useful books are also provided on this webpage. Further Reading and Other Resources Further Reading: Websites Cretaceous Atlas of Ancient Life An online guide to the types of fossils found in deposits from the Western Interior Sea, with photographs of many types of invertebrate and vertebrate fossil material. Managed by the Paleontological Research Institution as part of the Digital Atlas of Ancient Life project. Cretaceousatlas.org Oceans of Kansas Paleontology One of the most extensive sources of online information about life in the Western Interior Sea. This website is run by Mike Everhart, Adjunct Curator of Paleontology at the Sternberg Museum of Natural History in Hays, Kansas. It features lots of excellent information about all types of extinct animals from the Cretaceous of Kansas. Oceansofkansas.com Treatise on Invertebrate Paleontology An open-access 55 volume series from the University of Kansas Paleontological Institute detailing information about all known groups of prehistoric invertebrates. All volumes can be downloaded as pdf files from the Treatise website. Treatise on Invert Paleo website Animals of Ashfall, Nebraska Public Media Produced in collaboration with the University of Nebraska State Museum of Natural History. This website presents descriptions, illustrations and 3D models of some of the fossils of Miocene animals found at the Ashfall Fossil Beds in northern Nebraska. Animals of Ashfall Ammonites.org An online database with entries on hundreds of ammonoid and nautiloid species sorted by chronology and by their evolutionary relationships. Many entries have high quality photographs of cephalopod fossil specimens. Written in French. Ammonites.org Further Reading: Books Oceans of Kansas: Second Edition (2017) Written by Mike Everhart and published by Indiana University Press. This second edition builds on the original version of the book published in 2005. An excellent resource about the geology and paleontology of the entire Western Interior Sea Find this book Elephants and Their Fossil Relatives: A 60 Million Year Journey (2026) Written by Asier Larramendi and Marco P. Ferretti, illustrated by Shu-yu Hsu, published by Princeton University Press. A very comprehensive guide to all types of extinct proboscideans, featuring some excellent illustrations of these animals in their habitats. All of the proboscidean genera known from the Midwest are discussed in this book. A very good reference for anyone who wants to learn about the anatomy and ancient evolutionary history of extinct elephant relatives. Find this book Coloring Pages and Anatomical Diagrams We have produced a series of downloadable anatomical coloring pages for those who would like to learn more about the anatomies of prehistoric animals. Coloring pages featuring drawings of the animals themselves are also available. Learn more

Explore the types of Ichthyosaurs who lived in the Western Interior Sea, including animals like Athabascasaurus and Maiaspondylus Ichthyosauria Ichthyosaurs of the Western Interior Sea Ichthyosaurs were a group of marine reptiles whose streamlined bodies closely resembled those of modern dolphins. They had shark-like tail flukes, paddle-shaped limbs and often also had exceptionally large eyes that helped them to hunt effectively in low-light underwater environments. Unlike most reptiles, ichthyosaurs were viviparous, giving birth to live young in the ocean rather than laying eggs on land. During the Cretaceous Period, many of the surviving ichthyosaurs belonged to the platypterygiine lineage, a subgroup of ophthalmosaurid ichthyosaurs who managed to live on long after most other types of ichthyosaurs had long since gone extinct. Evolutionary History (BELOW) A group of large Ichthyosaurs has washed ashore during the late Triassic. During the mass extinction event at the end of this period, most of the larger types of ichthyosaurs would die out and vanish from the fossil record. An Ancient Group of Marine Reptiles Ichthyosaurs were one of the first major groups of reptiles to become fully adapted to life in the ocean. Their evolutionary history begins all the way back during the Early Triassic shortly after the end-Permian mass extinction. The terrestrial ancestors of this group gradually acquired a range of aquatic adaptations, first becoming semi-aquatic and then eventually fully marine animals. Throughout the middle and late Triassic period ichthyosaurs diversified dramatically. They developed their dolphin-like streamlined bodies and became important predators in marine ecosystems. Some species, including Shonisaurus, evolved enormous sizes and ranked among the largest marine reptiles of the era, growing to be larger than some of today’s sperm whales. Some of these ancient giants may have even evolved specialized jaw structures used for filter feeding. Ichthyosaur sizes reached their peak towards the end of the Triassic period but most of the larger groups of ichthyosaurs died out during the end-Triassic extinction event. The animals who made it through to the Jurassic period were generally smaller and more heavily built than the large, slender ichthyosaurs of the late Triassic period. They remained a key part of the ocean food web as generalists and even large macropredators all the way through the Jurassic, although they faced increased competition from other types of marine reptiles such as plesiosaurs. Although ichthyosaur diversity declined during the Cretaceous, the group continued to be represented by advanced members of the subfamily Platypterygiinae before they disappeared completely during the early part of the late Cretaceous. (BELOW) A fossil preserving the remains of the Cretaceous Ichthyosaur Maiaspondylus was found alongside the bones of two ichthyosaur embryos. These animals were unable to leave the water to lay eggs and so they instead gave live birth at sea. Platypterygiines (Platypterygiinae) The Last of the Ichthyosaurs Platypterygiines were a distinctive subgroup of ichthyosaurs that were some of the last Ichthyosaurs to exist before their extinction during the middle Cretaceous period. These animals are often grouped together based on the square-shaped tooth roots, specialized limb structures, and broad, powerful pectoral fins often seen in the members of the platypterigiine lineage. These adaptations likely helped them occupy a variety of predatory niches in Cretaceous marine ecosystems, msotly as soft-prey specialists. During the middle Cretaceous, North American seas were home to several platypterygiine taxa of various sizes, whose fossil remains are found in deposits located in Canada and Wyoming dating to a time before the two halves of the Interior Sea had fully joined together. Athabascasaurus Temporal Range: 112.6 million years ago - 109 million years ago Geographic Range: Alberta Species: A. bitumineus Diet: Carnivorous, fish, squid Athabascasaurus was an ichthyosaur that measured around 11 feet long which would have made it a medium-sized marine predator within the Cretaceous seas of North America. Its first fossils were found in 2000 at an oil sands mine near Fort McMurray, Alberta. The fossil included a nearly complete skull and most of an articulated skeleton which was enough material to tell that this animal should belong to a new genus. The name Athabascasaurus honors the Athabasca region where the specimen was discovered, while the species name bitumineus references its recovery from bitumen-rich oil sands deposits. Maiaspondylus Temporal Range: 113 million years ago - 94.3 million years ago Geographic Range: Northwest Territories, the UK, Russia Species: M. cantabrigiensis, M. lindoei Diet: Carnivorous, fish, squid Maiaspondylus is a platypterigiine ichthyosaur known from fossil material discovered in the Loon River Formation of northern Canada. It can be distinguished from other ichthyosaurs by its enlarged front flippers and widened upper arm bones which formed a large section of the point where its flippers articulated with the joints of its shoulders. The original material we now call Maiaspondylus was initially assigned to the genus Platypterygius , a genus which has since become considered a “wastebasket taxon” with many distantly related ichthyosaurs placed within this genus as new species. Many of these species have since been split into new genera of platypterigiines. Further study led to the fossil from the Loon River Formation being formally named Maiaspondylus in 2006. The genus name means “good mother vertebra”. This name was inspired by a fossil containing two embryos preserved alongside the remains of an adult individual. This specimen showed that Maiaspondylus, much like other ichthyosaurs, gave birth to live young at sea. Suggested References: Ichthyosauria Druckenmiller, P. S.; Maxwell, E. E. (2010). "A new Lower Cretaceous (lower Albian) ichthyosaur genus from the Clearwater Formation, Alberta, Canada". Canadian Journal of Earth Sciences. 47 (8): 1037–1053. Fischer, V; Maisch, M. W.; Naish, D ; Kosma, R.; Liston, J.; Joger, U.; Krüger, F.J.; Pérez J. P.; Tainsh, J; Appleby, R. M. (2012). "New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary". PLOS ONE. 7 (1) e29234. Naish, D. (2023). “Ancient Sea Reptiles: Plesiosaurs, Ichthyosaurs, Mosasaurs, and More. Washington, DC”: Smithsonian Books, 192 p Zverkov, N. G. ; Grigoriev, D. V. (2020). "An unrevealed lineage of platypterygiines (Ichthyosauria) with peculiar forefin structure and semiglobal distribution in the mid-Cretaceous (Albian–Cenomanian)". Cretaceous Research. 115 104550.

Coloring pages featuring prehistoric animals from the Midwest which can all be downloaded as pdf files! Browse this section for anatomical coloring pages to learn more about the skeletal structures of ancient animals. We also have coloring pages made from drawings of prehistoric animals in their natural habitats. Coloring Pages Free downloadable coloring pages featuring prehistoric life known from fossils found in the Midwest. The lower section of this page also features some anatomical diagrams which can be colored in to learn about the skeletal features of these ancient animals. Click on the links below to download these coloring pages as printable pdf files. Tylosaurus A giant mosasaur that once swam in the seas which covered the Great Plains during the late Cretaceous period. Tylosaurus is also the state ocean fossil of Kansas! Download pdf file Columbian mammoth One of the largest land animals to live in North America during the Pleistocene epoch. Download pdf file Pteranodon These huge flying reptiles were part of a group of animals called the pterosaurs who were some of the most abundant flying animals of the Mesozoic era, the time of the dinosaurs. Download pdf file American mastodon A type of elephant relative (proboscidean) known from fossils found across North America. They had cusped teeth used to chew up woody plants. Download pdf file Carboniferous period Invertebrates A selection of ocean invertebrates whose fossils are found in parts of eastern Kansas Download pdf file Cooperoceras A strange spiky nautiloid whose fossils are found in Texas, Oklahoma and Texas Download pdf file Giant bison Bison latifrons , the giant bison, was one of the largest bovids of all time, weighing about as much as a large rhino! Download pdf file Carboniferous period fishes Prehistoric fishes whose fossils are found in marine deposits in parts of the Midwest which were covered by shallow seas during the Carboniferous period Download pdf file Anatomical coloring pages Add color to these labeled diagrams to learn more about the unique skeletal features of prehistoric animals Nothrotheriops skeletal anatomy A coloring page of the skeletal anatomy of the Shasta ground sloth from the Pleistocene of the southwestern US. Click below to download the file. Download pdf file Protostega skeletal anatomy A coloring page of the skeletal anatomy of the sea turtle Protostega from the Cretaceous of Kansas. Click below to download the file. Download pdf file Batomorph skeletal anatomy A coloring page of the skeletal anatomy of an eagle ray, Myliobatis . Click below to download the file. Download pdf file Tortoise skeletal anatomy A coloring page of the skeletal anatomy a tortoise showing the placement of the bones beneath the shell. Click below to download the file. Download pdf file Mammoth skeletal anatomy A coloring page of the skeletal anatomy of a Columbian mammoth h from the Pleistocene of North America. Click below to download the file. Download pdf file Theropod cranial anatomy A coloring page of the anatomy of the skull of a Tyrannosaurid meat-eating dinosaur. Click below to download the file. Download pdf file Theropod skeletal anatomy A coloring page of the skeletal anatomy of a meat-eating theropod dinosaur, Gorgosauru s. Click below to download the file Download pdf file Platecarpus skeletal anatomy A coloring page of the skeletal anatomy of the mosasaur Platecarpus from the Cretaceous of Kansas. Click below to download the file. Download pdf file Ray-finned fish skeleton A coloring page of the skeletal anatomy a Pycnodont ray-finned fish from the Cretaceous period. Click below to download the file. Download pdf file Armadillo skeletal anatomy A coloring page of the skeletal anatomy of the a nine-banded armadillo, showing the bones of the animal as they appear beneath the shell. Click below to download the file. Download pdf file Plesiosaur skeletal anatomy A coloring page of the skeletal anatomy of a polycotylid plesiosaur and an elasmosaurid from the Cretaceous of Kansas. Click below to download the file. Download pdf file Dire wolf skeletal anatomy A coloring page of the skeletal anatomy of the a dire wolf from the Pleistocene of North America. Click below to download the file. Download pdf file Shark jaw anatomy A coloring page of the skeletal anatomy of the jaw cartilages of a shark. Click below to download the file. Download pdf file Ammonoid shell anatomy A coloring page of the shell anatomy of an ammonoid. Click below to download the file. Download pdf file Placoderm anatomy A coloring page of the skeletal anatomy of the placoderm fish Dunkleosteus from the Devonian period. Click below to download the file. Download pdf file Tortoise shell anatomy A coloring page of the different types of scutes found on the shells of turtles and tortoises. Click below to download the file. Download pdf file

The Giant Beaver Castoroides was one of the largest rodents ever to live in North America and would have lived in freshwater environments during the Pleistocene epoch Rodentia Giant Pleistocene Rodents Rodents are mammals characterized primarily by a single pair of continuously growing incisors in both the upper and lower jaws. These incisors are large and chisel-shaped, well adapted for gnawing through tough materials. Rodents lack canine teeth and typically have a distinct gap called a diastema between their incisors and their cheek teeth. Rodents include all of today's mice, rats, gerbils, guinea pigs and porcupines, but during the Pleistocene epoch some North American rodents reached massive sizes. In particular the Giant Beaver Castoroides may have been the largest rodent to live in North America. Giant beaver Castoroides ohioensis Temporal Range: 1.9 million years ago to approximately 11,000 years ago Geographic Range: Found across North America from the Yukon to Florida Species: C. ohioensis, C. dilophidus Diet: Herbivorous, grasses, aquatic plants Castoroides , commonly known as the giant beaver, was one of the largest rodents ever to live in North America. This massive mammal inhabited lakes, marshes, and wetland habitats. Its fossils have been discovered across much of North America, with one species most often found in the Midwest (C. ohioensis ) and another species found in the southeastern US (C. dilophidus ) Unlike modern beavers, Castoroides was enormous, reaching lengths of about 7 feet and weighing about as much as a small bear. Its body was heavily built, with large hind feet that likely aided with swimming. Their tails may have been longer and less paddle-shaped than those of living beavers. One of Castoroides ' most notable features was the size of its incisors, which could grow to be over 6 inches long. These teeth had a textured enamel surface not seen in the chisel-like incisors of modern beavers. Evidence suggests that Castoroides fed primarily on aquatic vegetation rather than cutting down large trees. (BELOW) A labeled diagram of the skeletal anatomy of the giant beaver Castoroides . Drawing is based on a mounted skeleton on display at the Joseph Moore Museum in Richmond, Indiana. Note the extremely large size of the incisors. (BELOW) A partial cranium of Castoroides displayed alongside the cranium of an extant beaver. These huge rodents could easily weigh 20 times more than their smaller relatives. Media Gallery Suggested References: Rodentia Harington, C.R. (2007). "Giant Beaver, Castoroides ohioensis, remains in Canada and an overlooked report from Ontario". Canadian Field-Naturalist. 121 (3): 330–333. Korth, William W (1994). “The Tertiary record of rodents in North America”. Springer. p. 145. Parmalee P. W.; Graham R. W. (2002). "Additional records of the giant beaver, Castoroides, from the Mid-South: Alabama, Tennessee, and South Carolina". Smithsonian Contributions to Paleobiology. 93: 65–71. Plint, Tessa; Longstaffe, Fred J.; Zazula, Grant (2019). "Giant beaver palaeoecology inferred from stable isotopes". Scientific Reports. 9 (7179): 1–12. Swinehart, Anthony L., and Richards, Ronald L. (2001) "Palaeoecology of a Northeast Indiana Wetland Harboring Remains of the Pleistocene Giant Beaver (Castoroides Ohioensis)." Indiana Academy of Science.