LIMNOSCELIS

extinct genus of primitive reptiles, among the earliest of the disputed labyrinthodont reptilian forms, that occurs as fossils in Early Permian rocks (those 258 to 286 million years old) of North America. It has been presented as a stem form from which the more advanced reptiles may have derived; another theory has Limnoscelis as an abnormal labyrinthodont amphibian. Limnoscelis was about 1.5 m (5 feet) long, with a robust skeleton and a rather long and solid skull. An opening for the pineal organ, which was in effect a third eye, was present between the parietal bones of the skull roof. The nostrils were placed well forward, and the margins of the jaws contained numerous sharp teeth. The anteriormost teeth were larger than the others and labyrinthine in internal structure. Teeth also were present on the bones of the palate. The body and tail were long, and the limb girdles were massive. In life, the limbs were splayed outward from the body in a sprawling pose, a relatively primitive reptilian condition.