Edaphosaurus boanerges
Synapsid
Early Permian
Ryan Formation
Jefferson County, Oklahoma, USA

Highly unusual 390mm tall vertebra with distinctive spine. Shown with standard ballpoint pens for scale.

Edaphosaurus was one of the early herbivorous vertebrates.  In life it would have looked like a reptile but was not a true reptile in that it occupies a taxonomic position within a general group, the synapsids, that led to mammals.  Like its rather-distant relative, Dimetrodon, it had a large sail on its back which was once interpreted as a means to regulate body temperature but it may had a display function, either to attract potential mates or intimidate rivals.

A well-prepared vertebra with a neural spine still attached is hard to find.