Petrolacosaurus

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Petrolacosaurus
Fossil range: Late Carboniferous

Petrolacosaurus kansensis

Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Subclass:	Diapsida
Order:	Araeoscelida
Family:	Petrolacosauridae
Genus:	Petrolacosaurus
Species:	P. kansensis

Binomial name

Petrolacosaurus kansensis

Petrolacosaurus was a small, 40 centimeter long, diapsid reptile, one of the earliest known. It lived during the late Carboniferous period 300 million years ago. The prehistoric reptile's diet may have consisted mainly of small insects. Petrolacosaurus had distinctive canine-like secondary-sized teeth, a trait found primarily in therapsids and later mammals.

A Mesothelae spider chasing a Petrolacosaurus eating a fly, as depicted in Walking With Monsters.

[edit] In popular culture

Petrolacosaurus was featured in the BBC television show Walking with Monsters. As well as claiming that it was the ancestral synapsid, the program states that its heart was the template for our own, even though the anatomy of Petrolacosaurus's organs and other soft tissue is completely unknown. It was portrayed as living alongside several species of giant arthropods, like giant Mesothelae spiders, and Meganeura, a giant dragonfly, as well as anthracosaur amphibians like Proterogyrinus.

However, because it was a primitive diapsid, it was not the common ancestor of either Dimetrodon, or Edaphosaurus. Both reptiles and Synapsids had a common ancestor. The ancestor of Dimetrodon was probably Haptodus, a primitive synapsid from 300 million years ago to 280 million years ago. Petrolacosaurus was a typical, albeit primitive, diapsid, having two openings ("temporal fenestrae") on each side of its skull to add attachment points for jaw muscles. Haptodus had one hole behind each eye socket, called the temporal fenestra.