EDAPHOSAURUS

extinct genus of primitive and highly distinctive early reptiles found as fossils in Late Carboniferous to Early Permian deposits of Europe and North America (the Carboniferous Period ended 286 million years ago and was followed by the Permian Period). Edaphosaurus was a large herbivore more than 3.5 metres (11 feet) long, with a short, low skull and conical and rather blunt teeth. The head was very small in comparison to the massive, barrel-like body. Perhaps the most distinctive feature of Edaphosaurus was a large dorsal sail that was formed by elongated dorsal vertebral arches probably connected by a membrane and that had bony knobs or crossbars along its length. It is not unlikely that the sail in Edaphosaurus functioned as a sort of temperature-regulating device. It is possible that the sail also may have served as a storehouse for phosphates needed in cellular energy exchanges and easily mobilized from the bony processes that make up the sail structure. The sail also may have been in part a defensive structure, giving the animal a larger and more imposing appearance to frighten away predators. It is thought that the growth, development, and maintenance of the sail placed a great strain upon the resources of the animal, however.