Edaphosaurus: Herbivorous Permian Pelycosaur

Edaphosaurus was a pelycosaur (early mammal-like reptile) that lived during the late Carboniferous and early Permian Period. It was a herbivorous relative of another pelycosaur, the well-known dimetrodon, and like dimetrodon had a large, thermal regulating sail on its back. Fossils of edaphosaurus have been found in Europe and North America.

Edaphosaurus was about 11 feet long and weighed more than 600 pounds. It was slightly taller and stockier than dimetrodon, but like its pelycosaur relatives had a small head and a long tail. The most striking feature of this herbivore was its sail, formed out of large bony spines projecting upward from its vertebrae. The bones were joined by a thin web of skin that was probably rich in blood vessels and unlike dimetrodon, the vertebral columns had crossbars that closed the gap between the spines in order to support the fin. This sail was most likely used in temperature regulation, allowing the edaphosaurus to warm up in the early morning in order to be active and feed, and cool down during the intense heat of the day. In the Permian world where the Earth was being subjected more and more to swinging temperature extremes, this adaptation would have made a favorable addition to reptilian survival techniques. Apart from temperature regulation, the sail could have been used for display purposes during mating or as a defensive measure against predators that might have mistaken an edaphosaurus for a larger animal due to the size of the prominent fin.

Also like dimetrodon, edaphosaurus had certain characteristics that have led scientists to classify them as synapsids. Synapsids include modern-day mammals and their reptile-like ancestors that lived before the age of dinosaurs. It is believed that edaphosaurus and other contemporary pelycosaurs evolved from small reptilian insect-eaters that lived during the preceding Carboniferous Period. Due to the structure of the skull and teeth of edaphosaurus, it is clear that it fed on plants rather than flesh, perhaps grazing in herds on the scrublands of the Permian in order to protect young. Edaphosaurs may well have been one of the earliest plant-eating mammals, altering its nutritional requirements and teeth in order to grind up and digest plants instead of meat for metabolism. The peglike teeth were well-suited for grinding up the course gymnosperm vegetation around at the time.

As conditions for life grew increasingly inhospitable on Earth during the Permian Period, edaphosaurus and many other pelycosaurs would not survive the drastic changes. As deserts widened and vegetation became more scarce on the supercontinent of Pangaea, more hardier animals would be the survivors of the worst mass extinction ever to strike our planet.