Kingdom Animalia
Phylum Chordata
Superclass Tetrapoda
Class Reptilia
Subclass Diapsida
Order Araeoscelida
Family Petrolacosauridae
Genus Petrolacosaurus
1st Species Petrolacosaurus kansensis
Other attributes
Time Range 302 mya
Location United States of America
Name Meaning Rock Lake reptile
Physical Dimensions 40 centimeters long
Dietary Classification Carnivore

Petrolacosaurus is a petrolacosaurid areoscelid reptile from the Pennsylvanian of the United States of America. It was named in 1945 by Henry H. Lane. It was one of the oldest diapsids to exist, and was originally thought to be a pelycosaur synapsid, before finally being discovered to be a diapsid reptile.


Petrolacosaurus resembled the generic lizard. It was a reptile with 4 legs, a long tail, a slender body (similar to that of an anole), and a head with mid-sized jaws. It body would have been covered in scaly skin.


Petrolacosaurus was a predator, feeding on small insects and other small arthropods. Its small and sharp teeth were used to get a hold of arthropod prey as the reptile swallowed them whole.


Not much is known about Petrolacosaurus, although it can be inferred that it lived very similarly to modern lizards, quickly scampering across through the swampy terrain and eating small arthropods whenever it was hungry, as well as climbing up trees and hiding in fallen logs in order to escape hungry predators.

In popular cultureEdit

Petrolacosaurus was featured in the 2nd episode of the 2005 documentary Walking with Monsters, where its eggs are shown evolving from Hynerpeton eggs over a course of 58 million years. As well as this, it is shown as the prey item of arthropod predators such as giant mesothele spiders, as well as Meganeura; despite this, it manages to get past the violent storm that destroys nearly all life in the area, fancifully and erroneously evolving into Edaphosaurus over a course of 22 (or 2) million years.

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