Hall of Vertebrate Origins


Anthracosaurs: extinct relatives of amniotes

Diadectes phaseolinus
 (DI-a-DEK-tes FAZ-e-o-LI-nus)
 ”Crosswise biter” 

The anthracosaurs that gave rise to the amniotes—true land animals with watertight eggs—probably looked something like Diadectes. Diadectes shows the general form of early amniote relatives: well-developed limbs clearly capable of terrestrial locomotion, but a posture that is sprawling, not erect, like that of many later amniotes. What Diadectes ate is unknown, but it had complex, molarlike teeth and may have been a plant-eater.

AMNH 4684, collected by E.C. Case, 1906, Godlin Creek, Archer County, Texas. Diadectes phaseolinus lived 280 million years ago.

Cricotus crassidens
 (kri-KO-tus KRAS-ih-dens)
"Ring [vertebrae]”

The anthracosaurs are important because they represent the earliest relatives of true land animals, the amniotes. Nonetheless, some of the most successful anthracosaurs were aquatic, with a long tail and fins for swimming. Cricotus is one of those aquatic anthracosaurs. It was presumably a predator, similar to crocodiles, living on fish and other fresh water animals. Some aquatic anthracosaurs were very large, reaching a length of more than 10 feet (3 meters).

AMNH 4550, collected by J. Boll, 1880, North Fork, Little Wichita River, Texas. Cricotus crassidens lived about 280 million years ago. 


Xiphactinus audax 
(zi-FAK-ti-NUS o-DAKS)
“sword ray [fin]” 

At the end of the age of dinosaurs, 85 million years ago in the Late Cretaceous era, a great inland sea covered most of what is now North America. Among the primitive life forms navigating those waters was Xiphactinus audax, a giant species of ray-finned fish. 

With its strong jaws and many teeth, Xiphactinus was undoubtedly a predator feeding on smaller aquatic creatures. Frequently, Xiphactinus fossils have been recovered with the remains of prey in their stomachs; leading scientists to characterize the Xiphactinus as a voracious predator that dominated the great sea of North America. This specimen was discovered in Logan County, Kansas


Geochelone atlas
(GE–o–ke–LON–ee AT–las)
“land turtle”

Two million years ago, the Geochelone could be found in warm climates across Asia, ranging from India to Indonesia. Though its relationship to today’s tortoises is clear, with its oversized shell and elephantine feet, the Geochelone grew to magnificent sizes rarely achieved by its contemporary cousins. An adult could reach an estimated total length of 8.2 to 8.9 feet and weigh at least a ton. 

This complete Geochelone specimen was collected by Barnum Brown in 1922 during an arduous expedition in the Siwalik Hills of India. At this point in his career, Brown was an Associate Curator at the Museum, and his work in India served as a forerunner of his significant collecting expeditions to come; the ample returns of this expedition—including this enigmatic Geochelone—brought the Museum’s Asian collections to new levels of prominence. 

Named for William H. Buettner 

Presented here is one of the few actual skeletons of Buettneria mounted for display in the world. By employing an inventive cylindrical casing, Museum preparators are able to offer visitors a sprightly portrait of this aquatic predator, its mount echoing the dynamism of underwater movement. 

The Buettneria roamed the waters during the Late Triassic period, some 225 million years ago. Its oversized, toothed skull and diminutive, nimble limbs recalls the modern crocodile, though it bears no direct relationship. The Buettneria, however, was certainly akin to the crocodile in its global distribution: its fossils and those of its close relatives have been found throughout North America, Europe, Africa, and Asia. This individual was collected on the grounds of the Herring Ranch in Potter County, Texas

Tylosaurus proriger 
(TI-lo-SOR-us PRO-ri-jer)
“knob [snout] lizard” 

Tylosaurus proriger was a large marine lizard closely related to modern monitor lizards and snakes that lived 85 million years ago in the Late Cretaceous. In its time Tylosaurus was a predator of note: a giant carnivore that feasted on a number of small fishes and other toothed aquatic animals. Tylosaurus evolved a number of adaptations for marine life, including a long tail for swimming, and flippered feet used for steering. 

This Tylosaurus was discovered in 1897 by famed dinosaur hunter W.G. Bourne in the sediment of Hell Creek, a small tributary Kansas’s Smoky Hill River. Well-preserved in its original matrix and position, this specimen is 28 feet long. 


Pteranodon longiceps
(te-RAN-o-don LON-ge-SEPS)
"toothless flyer"

With a wingspan of 23 feet, the agile Pteranodon was a master of the skies that could cover great distances with ease. Though a reptile, Pteranodon was not a dinosaur and, therefore, not a bird either, but it showed, the toothless beak and light, hollow bones that enable flight in modern-day birds. 

Paleontologists believe that Pteranodon lived on fish as it traversed the Earth’s primitive oceans in the Late Cretaceous era, some 85 million years ago. Pteranodon travelled such great distances that some fossils have been found in marine sediments at least 100 miles from land. This individual was collected in western Kansas.