Parareptilia

Long ago, there were old reptiles.

Some of them lived in the water.

Other kinds lived on land. Some were very big. They were as large as oxen!

Some reptiles could walk on two legs.

This helped them move in new ways.

Most of these animals are gone now. Only a few small ones lived a bit longer.

Scientists still study their old bones. It is fun to learn about them!

Parareptiles were a group of ancient reptiles.

They first appeared near the end of the Carboniferous period. Most lived during the Permian period. These animals were very different from each other.

Some parareptiles were the first to live in the sea. We call these mesosaurs.

Other kinds were the first to walk on two legs. One was named Eudibamus.

Some were very large plant eaters. The pareiasaurs were among the biggest. They grew to be as large as oxen!

Many parareptiles had solid skulls. This means they had few holes behind their eyes. Some had large holes, but most did not. Their bodies were often low and strong. Many had thick limbs and short toes.

Most parareptiles died out long ago. Only a small group called procolophonoids lived into the Triassic period. Scientists still study their bones. They wonder if turtles are related to parareptiles. This is still a big debate today.

Parareptilia is a group of ancient reptiles that lived a very long time ago.

They first appeared near the end of the Carboniferous period. Most of these animals thrived during the Permian period. Scientists call them "near-reptiles" because they are a group of basal sauropsids. These are early types of reptiles that are related to the animals we see today. They were very important because they were the first to try many new ways of living.

These animals showed us how reptiles could change to fit different worlds. The mesosaurs were the first reptiles to return to life in the sea.

Another group called bolosaurids, like Eudibamus, were the first to walk on two legs. Some parareptiles even had the first advanced hearing systems. The pareiasaurs were the first large reptiles that ate only plants. These large plant-eaters could grow to be as big as oxen.

Learning about these animals has been a big job for scientists. A man named Olson first used the name Parareptilia in 1947. For a long time, people did not study them very much. They often put these animals into a group called "anapsids." This was a name for reptiles with solid skulls that had no holes behind the eyes. In the 1990s, scientists started looking at them much more closely. This new interest helped people understand how they fit into the history of life.

Parareptiles had very interesting bodies and skulls. Many had low, strong bodies and thick limbs.

Their skulls were often different from other reptiles. Most had large eye sockets that were longer than the back of the head. Some had very large bones at the back of the skull called supratemporals. While many had solid skulls, some species actually had large holes behind their eyes. Their teeth also changed a lot depending on what they ate.

Today, scientists still have big questions about these ancient creatures. One big debate is whether turtles are part of the Parareptilia group.

Some studies in the 1990s suggested that turtles were related to them. However, newer studies using DNA suggest turtles might be related to birds and crocodiles instead. This means the solid skulls of parareptiles might just look like turtle skulls by chance. We are still learning how these amazing animals truly lived.

Parareptilia is an extinct subclass of basal sauropsids, which are early reptiles.

They are often called "near-reptiles" because of their relationship to other reptile groups. These animals first appeared near the end of the Carboniferous period. They reached their highest level of diversity during the Permian period. Scientists have debated whether Parareptilia is a monophyletic clade. A monophyletic clade is a group that includes a single ancestor and all its descendants. Some modern studies suggest they might actually be a paraphyletic grade. This means they are a group of primitive reptiles that do not all share the same immediate descendants.

These ancient animals were pioneers of many ecological niches.

The mesosaurs were the first reptiles to return to marine ecosystems. This means they moved from living on land back into the ocean. The bolosaurids, such as Eudibamus, were the first bipedal reptiles. Bipedal means they could walk on two legs instead of four. Some groups, like the nycteroleterids, developed the first advanced hearing systems. The pareiasaurs were the first large herbivorous reptiles. These plant-eaters were massive, with some reaching the size of modern oxen.

Parareptilian skulls show incredible variety. Some, like the mesosaurs, had elongated snouts filled with hundreds of thin teeth. Others, like the pareiasaurs, had snub-nosed skulls covered in knobs. Most parareptiles had large orbits, which are the sockets that hold the eyes. These orbits were often longer from front to back than the region behind the eyes. Many species had large supratemporal bones at the back of the skull. While they were traditionally called "anapsids" because of their solid skulls, this is not always true. Some parareptiles actually possessed an infratemporal fenestra. This is a large hole or opening located among the bones behind the eye.

Their body structures were also quite distinct.

Early members often had a lizard-like appearance with thin limbs and long tails. However, the most successful groups, like the procolophonids, had much stouter bodies. These animals had thick limbs and reduced tails. Many parareptiles had vertebrae with a "swollen" appearance. This means the upper surfaces of their spinal bones were wide and convex. Their hip bones, called ilia, were often fan-shaped and oriented vertically. This was an unusual trait compared to other early amniotes. Most had short, thick humerus bones that were wider near the elbow.

The history of how we classify these animals is complex. In 1947, a scientist named Olson coined the name Parareptilia. For a long time, these animals were poorly studied. They were often placed into a "wastebasket taxon" called Cotylosauria. This was a group used for many stout-bodied primitive reptiles. In the 1980s, researchers like Gauthier used cladistic studies to redefine these groups. They argued that the term Parareptilia should be used for specific clades. This helped move away from the older, less accurate term "Anapsida."

One of the most famous debates involves the classification of turtles, or Testudines.

In the 1990s, some studies suggested turtles were members of Parareptilia. If this were true, Parareptilia would not be entirely extinct. However, many other scientists disagree. Modern genetic analyses, such as a 2013 study by Wang et al., suggest a different path. This research indicates that turtles are likely a sister group to crocodilians and birds. This group is known as Archosauria. This means the solid skull of a turtle and a parareptile might be a result of convergent evolution. Convergent evolution happens when different animals develop similar traits independently.

Understanding Parareptilia helps scientists map the entire tree of life.

By studying their bones and teeth, we see how reptiles first adapted to different environments. We see how they moved from land to sea and how they learned to eat plants. Even though most parareptiles died out by the end of the Triassic period, their legacy remains. The procolophonoids were the only group to survive into the Triassic. They were small, lizard-like animals that could eat many different types of food. Their story shows how life constantly changes and finds new ways to survive.