Parareptilia

Parareptilia, meaning "near-reptiles," was an extinct subclass of basal sauropsids, which are often called reptiles. Scientists have debated whether this group truly belongs together as a single family. These ancient creatures first appeared near the end of the Carboniferous period and became most diverse during the Permian period.

Parareptiles were responsible for several important firsts among reptiles. They were the first reptiles to live in marine environments, like the mesosaurs. Some, such as bolosaurids like Eudibamus, were among the first to walk on two legs. Others developed better hearing, and the large pareiasaurs were the first big plant-eating reptiles, growing as large as oxen. Only a few types, called procolophonoids, survived into the Triassic period.

Compared to their relatives, parareptiles kept more basic body shapes, with strong, low bodies and large bones at the back of their skulls. Most had simpler skull structures than other reptiles, though not all fit older definitions. They also had special features like a large pit on their upper jaws.

Scientists became more interested in parareptiles in the 1990s when some suggested that turtles might actually belong to this group. However, this idea is still debated, as many studies place turtles closer to other reptile groups. Recent research from the early 2020s suggests that Parareptilia may not be a single family but instead a mix of early reptiles.

Description

Parareptilian skulls came in many shapes, from mesosaurs with long snouts full of tiny teeth to pareiasaurs with short, knobby skulls. Their teeth varied a lot between species but were usually similar on the same skull. Unlike many other early reptiles, most parareptiles did not have large fang-like teeth at the front of their mouths.

These reptiles often had a few small pits along the edges of their mouths, with one big pit near the front. Their skulls were usually rough, with pits, ridges, and bumps. The bones around their eyes were large, and many had a special hole where certain bones met. Their jaws were often short and thick, except for mesosaurs, which had long, slender jaws.

The bodies of parareptiles also varied. Early ones looked like lizards with thin legs and long tails. Later, successful groups like pareiasaurs and procolophonids had sturdy bodies with short tails and strong, short legs. Their backbones had wide, rounded vertebrae.

Parareptiles did not have a certain hole in their shoulder bones that many other early reptiles had. Their upper arm bones were short and thick, and their lower leg bones were usually not much longer than their upper ones. Some, like Eudibamus, an early Permian bolosaurid, had very long back legs.

History of classification

The name Parareptilia was created by Olson in 1947 for an extinct group of ancient reptiles from the Paleozoic period, different from what we call "true reptiles" or Eureptilia. At first, scientists did not use this name much and grouped these creatures in other ways.

Later, with new ways of studying family trees, scientists brought back the name Parareptilia. They used it for early reptiles from the Permian and Triassic periods that did not belong to a group called Anapsida. Different scientists have had different ideas about how these reptiles are related. Some thought turtles were part of Parareptilia, while others thought turtles were more closely related to lizards and crocodiles. Recent studies suggest that Parareptilia might actually belong within a larger group called Diapsida, meaning these ancient reptiles shared features with modern reptiles through similar evolution.

Evolutionary history

The oldest known "parareptiles" are from the Late Carboniferous period in North America. Many different groups of "parareptiles" appeared during the early Permian period and spread around the world. By the end of the Permian period, only one group, called procolophonoids, survived a big event that changed the Earth. This group then disappeared by the end of the Triassic period.