Petrolacosaurus is a small synasaur reptile and was one of the first reptiles. It hunted insects. This creature was probably hunted in turn, by giant solifugids, such as the Solifugid Mesothelae.
Walking with DinosaursEdit
It didn't even appeared in Walking with Dinosaurs.
Walking with MonstersEdit
After the baby Hynerpeton get on dryland in the Carboniferous, they evolve into the first reptiles. However, as most leave their nest, those who are left behind are watched by a female Mesothelae and she stands on 2 legs before attacking.
An adult Petrolacosaurus was killed by Mesothelae by injecting her digestive juices into him. As she drags her dinner home, her headquarters are flooding and she will have to evacuate. As she moves with her dinner to find a new hole, a gigantic female dragonfly called Meganeura has stealed her dinner. After Mesothelae sees Proterogyrinus, other Mesothelae, and an Arthropleura, she finds another hole and another Petrolacosaurus comes out of her hole and leaves. Mesothelae settles in her new home and the storm continues, whcih causes a huge fire that has burned the forset, but a Petrolacosaurus has managed to outrun the flames. He heads right into the spider's lair. He comes out of the burrow with the female Mesothelae that was killed by the lightning strike.
A spider roast is served for the reptile. Later, Petrolacosaurus evolves into a supgroup called therapsids which included Dimetrodon and Edaphosaurus (this is impossible, as Petrolacosaurus was a diapsid reptile, related to modern lizards, snakes, crocodiles, and birds, whereas Edaphosaurus was a synapsid, related to modern mammals).