The forty-foot mosasaur takes a huge bite out of an 800-pound “bulldog tarpon,” its large eyes warily watching an enormous shadow a hundred yards away. There’s nothing to worry about; it’s merely another species of mosasaur feeding on hard-shelled ammonites.
With their light, flexible skulls and snake-like double-hinged jaws — inherited from the monitor lizards they evolved from — the mosasaurs are well adapted to swallowing large chunks of meat. Like crocodiles, they swim with their powerful tails, steering with their paddles. Like the sharks they swim among, their teeth are constantly replaced.
The mosasaur feeding on the bulldog tarpon bears an enormous scar on its flipper it received in a fight with another mosasaur. The scar on its tail was created by an enormous shark. The blood trailing from the bulldog is already attracting sharks, though they’re too small to threaten the mosasaur.
Numerous bulldog tarpon are in the area feeding on a massive school of smaller fishes, which have attracted a variety of predators. Pterosaurs soar overhead, like giant, bewitched pelicans, swooping down to pluck fishes from the sea or to grab bits of flesh from the bulldog tarpon.
The pterosaurs are joined by birds with feathers — and teeth! Ichthyornis resembles a tern or gull. A flock of flightless, loon-like Hesperornis measuring six to seven feet in length have joined the fray. Occasionally, a shark or bulldog tarpon lunges at a pterosaur or bird.
Still another mosasaur species is diving to the seafloor in search of shellfish, similar to the sea otter of the future. But it won’t touch any adult giant oyster (Inoceramus), which may measure several feet in diameter. Is great weight is supported among flower-like crinoids on the seafloor by its great size, like a snowshoe.
It’s really a pretty ordinary day in the Cretaceous seas over Kansas, some 70 million years ago.
Geology & Fossils
Fans of The Wizard of Oz know there’s no place like Kansas. It’s fossils are as famous as its sunflowers and tornadoes.
Although Kansas is one of the flattest states, it isn’t perfectly flat. It slopes downward from the northwest towards the Missouri River and the distant Gulf of Mexico. And some of the rock blankets, or formations, beneath Kansas tilt slightly downward in the opposite direction.
Looking down on perfectly flat land is like looking at a page in a book — the same kinds of fossils might be found everywhere. But thanks to Kansas’ gentle slopes and erosion, fossils from various chapters of Earth’s history are exposed.
The Kansas prehistory book is divided into three units, the last one unfinished. The rocks in eastern Kansas lie mostly within the Central Lowlands that cover so much of the Midwest. These rocks tell the story of Kansas during the ancient Paleozoic Era. In central and western Kansas, paleontologists study fossils from the Mesozoic Era, the Age of Dinosaurs. The unfinished unit is that of the Cenozoic Era, or Age of Mammals, in which we live.
Paleozoic Era
The book begins with rocks from the Pennsylvanian Period that underlie the Osage Plains of easternmost Kansas. Limestones are among the clues that Kansas was often underwater more than 280 million years ago. Crinoid stem parts are among Kansas’ most common Pennsylvanian marine fossils.
Extensive coal deposits have been mined throughout eastern Kansas. The remains of ancient plants, they remind us that Kansas wasn’t always underwater during the Pennsylvanian. Camping in a Kansas coal forest might have been dangerous — a track found in Kansas is believed to have been made by a six-foot-long centipede!
To the west, the Flint Hills mark the final chapter in Kansas’ PALEOZOIC unit. The rocks under this region date back more than 230 million years to the Permian Period. During the Permian, much of Kansas was again covered by seas.
Cretaceous Seas
Kansas is best known for its fossils from the Cretaceous Period, the last chapter of the Mesozoic Era — the Age of Dinosaurs. (A few small outcrops representing the older Jurassic Period are found in the southwest corner of the state.) But these fossils are buried in the chalk for which the Cretaceous is named, chalk that was laid down in ancient seas.
The Cretaceous chapter begins in the eroded badlands of north-central Kansas’ Smoky Hills. In the eastern range, pioneers dug up lignite — a cheap grade of coal — for heating their homes and for other purposes. In the middle range, they cut limestone into fenceposts because wood was scarce in the treeless land.
In the western range of the Smoky Hills, explorers and settlers first encountered Castle Rock and Monument Rocks, famous landmarks carved out of chalk deposited by ancient seas. Few pioneers imagined they were also landmarks in time, tombstones for fantastic creatures buried beneath their feet.
Here people have found the remains of winged pterosaurs, giant marine mosasaurs, feathered birds that boasted teeth, diverse fishes and invertebrates, and scattered dinosaurs that were washed out to sea. A sea of petroleum, a souvenir of ancient marine animals, rests beneath Kansas’ chalk.
Let’s meet some of Kansas’ ancient inhabitants.
Mosasaurs
Growing to lengths of ten feet or more, the Komodo dragon is capable of eating scientists who study it on its Indonesian islands home. It is the largest living monitor, which are in turn the largest living lizards. Replace the Komodo dragon’s legs with paddles and triple its size and you have some idea of a mosasaur.
Tylosaurs were mosasaurs that had unusually heavy teeth and a muzzle shaped like a blunt prow. A damaged fossil suggests they may have rammed their prey — or perhaps even other mosasaurs.
Diamond-shaped scales and tiny bony plates that strengthened the walls of their eyes characterize the finest mosasaur fossils. These come from western Kansas and reach lengths of thirty feet. Jaws and teeth found in New Jersey suggest a 45-foot giant mosasaur.
Kansas Turtles
Kansas’ official state reptile, the ornate box turtle, is far smaller than Archelon. One of the largest known turtles, this sea turtle grew to lengths of twelve feet. Like the largest living sea turtle, the leatherback, Archelon had lost most of its shell, covering its bones with tough skin.
A fine Archelon skeleton discovered in Kansas is missing a hind paddle. Was it bitten off by a mosasaur or shark, or was it simply nipped off by a prehistoric crab when it was young?
Pterosaurs
Nowhere are pterosaur fossils more common than in Kansas chalk. But the fossils are often damaged, because pterosaurs had light, hollow bones similar to birds.
Birds
Hesperornis resembled modern loons, which are considered among the most primitive birds. (Loon fossils have been found dating to the Paleocene Epoch, more than 50 million years ago.) Like loons, Hesperornis had heavy bones and probably walked poorly on land, if at all, because its legs were set so far back. Unlike loons, Hesperornis couldn’t fly.
Like other toothed birds, Hesperornis and Ichthyornis died out with the dinosaurs. Scientists think they left no descendants, as modern birds evolved from other prehistoric birds.
Sea Wheat
Prehistoric wheat is common in Pennsylvanian rocks in eastern Kansas — NOT! What appear to be wheat grains are actually fusulinids. Scientists even call one species Triticites, “wheat” in Latin.
Fusulinids were in turn types of foraminifera that became extinct during the Triassic Period, around 200 million years ago. But thousands of other types of Foraminifera still float in sea, growing to amazing sizes for one-celled organisms.
Marine Dinosaurs?
Rivers or floods occasionally washed dinosaurs out into Cretaceous seas. The only known skeleton of a duck-billed dinosaur called Claosaurus was found in Kansas chalk. Bones have also been found from Sylvisaurus and Heirosaurus, whose armor were no protection against drowning.
A Fishy Fossil
With giant mosasaurs, sea turtles, and pterosaurs, it’s hard deciding what Kansas’ most spectacular prehistoric animal was. But Kansas’ most famous fossil may be one with a split personality. Some 90 million years ago, a large fish called Xiphactinus swallowed a smaller Gillicus. But the larger fish died before it could digest its prey, and both were swallowed by Cretaceous chalk. The “fish within a fish” is now displayed in the Sternberg Memorial Museum in Fort Hays, not far from where it were discovered in 1952. (See a Picture)
Cenozoic Era
From the Smoky Hills the High Plains of western Kansas slope upward towards the Rocky Mountains in neighboring Colorado, interrupted by sand dunes along the Cimarron and Arkansas rivers. In fact, the High Plains are the Rocky Mountains. The soil and sand dunes began as rocks in the mountains eroded by rain and wind and blown or washed downward on to the plains below.
In other words, sediments were deposited on the Great Plains. But the opposite process also occurred. As the land was uplifted, Kansas’ ancient chalk seas dried up and the rate of soil erosion increased.
Here and there, older Cenozoic Era rocks peek out from under sediments from the Rocky Mountains. Rocks from the Miocene Epoch are exposed along stream banks in western Kansas, for example.
And many fossils from the Pleistocene Epoch, or Ice Age, have not been eroded away yet. In fact, many of them are covered only by boulders and dust left by glaciers. Ice Age glaciers covered only the northeastern corner of Kansas. But wind and rivers carried gravel and loess — or glacial dust — across the region, leaving especially thick loess drifts in the High Plains of western Kansas and the Great Bend Prairie of central Kansas.
Ash from volcanoes erupting far to the west was also blown over Kansas. Other sediments were drifted into sand dunes that are now mostly anchored with grasses.
Bones of Ice Age camels, horses, ground sloths, and muskoxen aren’t that unique. But a giant prehistoric bison on display at the University of Kansas’ Museum of Natural History is said to be the first North American fossil found in association with a human artifact. Scientists found a spear point between its ribs.
Kansas Geological Map
The upper picture looks down on Kansas as if you were flying over the state in a jet and had X-ray vision. The lower picture is what you might see if could cut Kansas in half and look at it from the side.
On the upper picture, the purple color at right (eastern Kansas) indicates rocks from the Pennsylvanian Period. The light blue color next to it represents the younger Permian Period (the last period in the Paleozoic Era).
The green area at top center is the Cretaceous chalk beds that Kansas is so famous for. The reddish streaks at left are rocks from the Cenozoic Era (the Age of Mammals). The yellow areas on the left (“loess and river valley deposits”) represent sediments from the Rocky Mountains to the west and Ice Age glaciers to the east that were deposited to form Kansas’ High Plains.
Compare this map to the Kansas Geological Survey’s Physiographic Map of Kansas.
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