Prehistoric Life During the Permian Period

The Permian period was, literally, a time of beginnings and endings. It was during the Permian that the strange therapsids, or "mammal-like reptiles," first appeared--and a population of therapsids went on to spawn the very first mammals of the ensuing Triassic period. However, the end of the Permian witnessed the most severe mass extinction in the history of the planet, even worse than the one that doomed the dinosaurs tens of millions of years later. The Permian was the last period of the Paleozoic Era (542-250 million years ago), preceded by the Cambrian, Ordovician, Silurian, Devonian and Carboniferous periods.

Climate and Geography

As during the preceding Carboniferous period, the climate of the Permian period was intimately linked with its geography. Most of the earth's land mass remained locked up in the supercontinent of Pangea, with remote offshoots comprising present-day Siberia, Australia, and China. During the early Permian period, large portions of southern Pangea were covered by glaciers, but conditions warmed considerably by the beginning of the Triassic period, with the reappearance of vast rain forests at or near the equator. Ecosystems around the globe also became significantly drier, which spurred the evolution of new types of reptiles better adapted to cope with the arid climate.

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Terrestrial Life During the Permian Period

• Reptiles: The most important event of the Permian period was the rise of "synapsid" reptiles (an anatomical term denoting the appearance of a single hole in the skull, behind each eye). During the early Permian, these synapsids resembled crocodiles and even dinosaurs, as witness famous examples like Varanops and Dimetrodon. By the end of the Permian, a population of synapsids had branched off into therapsids, or "mammal-like reptiles"; at the same time, the very first archosaurs appeared, "diapsid" reptiles characterized by the two holes in their skulls behind each eye. A quarter of a billion years ago, no one could have predicted that these archosaurs were destined to evolve into the very first dinosaurs of the Mesozoic Era, as well as pterosaurs and crocodiles!
• Amphibians: The increasingly dry conditions of the Permian period were not kind to prehistoric amphibians, which found themselves out-competed by more adaptable reptiles (which could venture further onto dry land to lay their tough-shelled eggs, whereas amphibians were constrained to living near bodies of water). Two of the most notable amphibians of the early Permian were the six-foot-long Eryops and the bizarre Diplocaulus, which looked like a tentacled boomerang.
• Insects: During the Permian period, conditions weren't yet ripe for the explosion of insect forms seen during the ensuing Mesozoic Era. The most common insects were giant cockroaches, the tough exoskeletons of which gave these arthropods a selective advantage over other terrestrial invertebrates, as well as various types of dragonflies, which weren't quite as impressive as their plus-sized forebears of the earlier Carboniferous period, like the foot-long Megalneura.

Marine Life During the Permian Period

The Permian period has yielded surprisingly few fossils of marine vertebrates; the best-attested genera are prehistoric sharks like Helicoprion and Xenacanthus and prehistoric fish like Acanthodes. (This doesn't mean the world's oceans weren't well-stocked with sharks and fish, but rather that the geologic conditions didn't lend themselves to the fossilization process.) Marine reptiles were extremely scarce, especially compared to their explosion in the ensuing Triassic period; one of the few identified examples is the mysterious Claudiosaurus.

Plant Life During the Permian Period

If you're not a paleobotanist, you may or may not be interested in the replacement of one weird variety of prehistoric plant (the lycopods) by another weird variety of prehistoric plant (the glossopterids). Suffice it to say that the Permian witnessed the evolution of new varieties of seed plants, as well as the spread of ferns, conifers, and cycads (which were an essential source of food to the reptiles of the Mesozoic Era).

The Permian-Triassic Extinction

Everyone knows about the K/T Extinction Event that wiped out the dinosaurs 65 million years ago, but the most severe mass extinction in earth's history was the one that transpired at the end of the Permian period, which annihilated 70 percent of terrestrial genera and a whopping 95 percent of marine genera. No one knows exactly what caused the Permian-Triassic Extinction, though a series of massive volcanic eruptions resulting in a depletion of atmospheric oxygen is the most likely culprit. It was this "great dying" at the end of the Permian that opened up the earth's ecosystems to new kinds of terrestrial and marine reptiles, and led, in turn, to the evolution of dinosaurs.