2.2" Rare, Fossil Plesiosaur Vertebra - Kansas

This is the vertebra of a Plesiosaur from the Niobrara Formation of Gove County, Kansas. It is 2.2" wide and the processes and cortical bone have weathered away. There are a variety of Plesiosaur genera that are found within the Niobrara Formation, making it difficult to confidently identify an individual vertebra such as this.

Plesiosaurs were aquatic reptiles. They had small heads, long necks, broad, flattened bodies, short tails and large flippers or paddles. It is one of the best described groups of fossil animals with a total of 110 known species, many from complete or nearly complete fossils. The largest known is Elasmosaurus, 40 feet (12 m), the smallest was Thalassiodracon at just under 6 feet (1.5m). They first appear in the fossil record near the end of the Triassic Period. Thalassiodracon is the oldest known from about 203 million years ago. It was about 6 feet long and showed all the characteristics of Plesiosaurs. They disappear from the fossil record about the time of the Cretaceous-Paleogene Extinction, along with the Dinosaurs and most other reptiles.

Plesiosaurs were almost comical in their appearance; small head full of sharp, cylindrical teeth, wide, comparatively flat bodies, short tails and four large paddles or flippers. It was so odd looking that when originally found it was mistaken for a new kid of Pterosaur. Even when the first Plesiosaur went on display, it had its head mounted on the wrong end. It was mounted on the tail. Plesiosaur necks could have large numbers of vertebrae. Albertonectes had 72 vertebrae in its neck. Plesiosaurs swam by moving their paddles or flippers in much the same way that modern sea turtles. This would have made them efficient and maneuverable but not particularly speedy. Due to their long, thin necks and flippers, it is unlikely that Plesiosaurs left the water. If they did, they would not have been able to travel far. It had long been thought that Plesiosaurs left the water to lay eggs in much the same way as modern sea turtle. Recent evidence seems to prove they bore live young. This would make leaving the water less likely. It is widely held that plesiosaurs were not the fastest swimmers in the sea. It is likely that they ate a wide variety of fish, squid and other mollusks.

An artists reconstruction of Plesiosaurus dolichodeirus.  By Dmitry Bogdanov  Creative Commons License
An artists reconstruction of Plesiosaurus dolichodeirus. By Dmitry Bogdanov Creative Commons License

Plesiosaur fossils have been found worldwide. The first described fossil was found in Kansas. Since then they have been found on every continent. Most commercially available Plesiosaur fossils come from Morocco and Kansas.

The Smoky Hill Chalk Member of the Niobrara Chalk formation is a Cretaceous conservation Lagerstätte, or fossil rich geological formation, known primarily for its exceptionally well-preserved marine reptiles. It outcrops in parts of northwest Kansas, its most famous localities for fossils, and in southeastern Nebraska. Large well-known fossils excavated from the Smoky Hill Chalk include marine reptiles such as plesiosaurs, large bony fish such as Xiphactinus, mosasaurs, pterosaurs, and turtles.
Unidentified Plesiosaur
Gove County, Kansas
Niobrara Formation
2.2" wide
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