The enigmatic Edaphosaurus, aka the "pavement lizard," will not be  tread on! Like many other prehist- oric critters, there were several species of Edaphosaurus that spanned across multiple geologic periods: from the Carboniferous to the Permian. The largest species could grow to an impressive three meters long! Despite sporting a similar sail to the Permian predator Dimetrodon, Edaphosaurus was  actually a gentle herbivore. The  name "pavement lizard" refers to its densely-packed teeth, which sat in deep jaws that sported mighty muscles. Ferns must have quivered  with fear when they saw the formid- able Edaphosaurus appear!  During the Carboniferous, Edapho- saurus lived in iconic rainforests called coal forests (named for the fact that its plant matter became coal). The species that lived in the  Permian period still inhabited lush  marshes, but experienced gradual  global warming and drying as the  planet transitioned to hot, dry  deserts. Although some researchers  hypothesized that its large sail was useful for cooling the body, it was likely used for either fat storage  or display instead. The "pavement lizard" paraded its sail across a  large range, extending across much  of the modern United States, only  vulnerable to falling prey to large predators like Dimetrodon.