August 12. Permian amphibians

Although amphibians suffered in the collapse of the Carboniferous rainforest ecosystem just before the end of the Carboniferous, they did adapt enough to survive into the Permian.  Since the primary information about fossil vertebrates comes from their bones, it can be difficult to separate the early amphibians, reptiles, and mammals from each other based on fossil evidence, but with more and more discoveries, the branches are becoming clearer. Some groups that were formerly considered to be reptiles are now thought of as amphibians. 

Eryops, a terrestrial-adapted temnospondyl amphibian about 5 feet long.

One such group, the Temnospondyls, have been found in enough diversity that we consider them today to be amphibians. These guys were diverse, often relatively large animals pretty much like crocodiles in body form, but they lived in environments ranging from fully aquatic to fully terrestrial. Temnospondyls got their start in the late Carboniferous and during the Permian became fully adapted to life on land. As things became drier during the course of the Permian, the terrestrial varieties seem to have declined, but aquatic types thrived, and in fact the largest amphibian known is from the Permian. It’s called Prionosuchus and its fossils were found in Brazil, where it lived in tropical lagoons and river systems. It was as much as 9 meters or 30 feet long, and looked much like a crocodile. That particular genus was extinct by the end of the Permian, but Temnospondyls generally survived the Permo-Triassic extinction and continued into the Cretaceous. Evolutionary branches of the temnospondyls probably gave rise to modern toads and frogs sometime during the Triassic, but that history isn’t certain.

There are quite a few amphibians known from the Permian, but most are from the early Permian. A lot of them were little lizard-like critters, and some were almost snake like. The Aïstopods – a name meaning “no visible feet” – had a couple hundred vertebrae but some were only a few inches long. Some aquatic Permian amphibians had wide heads shaped like boomerangs that might have helped them swim, though to be honest it seems to me that we don’t really understand these head ornamentations. Microsaurs, whose name means “small lizards,” were around by Permian time, and they may be the ancestors of modern salamanders and newts. There’s really quite a large diversity of amphibians from the Permian, but many of them are known only from one specimen – so figuring out their interrelationships can be pretty challenging.

By mid- to late Permian, conditions were no longer favorable for amphibians, or perhaps conditions were just not favorable for preservation of their fossils. Or some combination of both. Amphibians obviously have survived to the present, so they must have found some niches where they were able to thrive, or at least hang on, for millions of years.

—Richard I. Gibson

Eryops, a terrestrial-adapted temnospondyl about 5 feet long. Photo by Daderot (public domain)