Sauria

Many animals belong to this group.

It includes birds and crocodiles.

Snakes and lizards are also in it. Turtles are part of this group too. Scientists found this by looking at bones. They also looked at tiny parts of cells. This group has lived for a long time. Many of these animals are still alive today.

Sauria is a large group of animals.

It includes many animals we see today. This group has birds and crocodiles in it. It also has snakes and lizards.

Some scientists think turtles belong here too. They found this by studying DNA. DNA is the code inside living cells. They also looked at old fossils.

In the past, people used the name Sauria differently. Long ago, it only meant lizards and snakes. Now, scientists use it for a much bigger family. This family starts with a common ancestor. An ancestor is a very old relative. This relative is the start of two main lines. One line leads to birds and crocodiles. These are called archosaurs. The other line leads to lizards and snakes. These are called lepidosaurs. Sauria includes all the animals from these lines. It also includes many animals that are now extinct. This means they died out a long time ago.

Sauria is a very important group of animals. It is a large family that includes many living things. This group contains archosaurs, which are birds and crocodilians. It also includes lepidosaurs, like snakes and lizards.

Some scientists think turtles are part of this family too. This makes Sauria a major part of the reptile world. It helps us understand how different animals are related.

Scientists define Sauria by looking at a common ancestor. This ancestor is the starting point for two main paths. One path leads to birds and crocodiles. The other path leads to lizards and the tuatara. To find these links, scientists look at body parts. They check the skull and the ribs. They even look at the tiny bones in the limbs. These traits help show how the group works together.

In the past, the name Sauria meant something different. During the 18th century, it was used for a smaller group. Back then, it mostly described lizards and crocodilians. This changed in the 1980s because of new research. Jacques Gauthier and his colleagues redefined the name.

They used the name to describe the last common ancestor of archosaurs and lepidosaurs. This made the group much larger than before.

Many studies have helped us learn about these animals. In 2012, a study by Nicholas G. Crawford used DNA. This study suggested that turtles are closely related to archosaurs. Another study in 2013 by M.S. Lee looked at fossils. Lee found that a creature called Eunotosaurus is only distantly related to turtles.

Other scientists like Rainer Schoch and Hans-Dieter Sues studied fossils in 2015. They had different ideas about how these animals fit together.

Learning about Sauria helps us see the big picture of life. It connects the animals in your backyard to huge prehistoric creatures. You might see a lizard or a bird today. These are all part of this ancient family tree.

Even extinct animals like the ones in the fossil record fit here. By studying these connections, we learn how life changes over time. It shows us how one ancestor can lead to so many different forms.

Sauria is a major biological group known as a clade. A clade is a group of animals that all share a single common ancestor.

In biology, Sauria represents the most recent common ancestor of two massive groups. These groups are Archosauria, which includes birds and crocodilians, and Lepidosauria, which includes snakes, lizards, and the tuatara. Because of these connections, many scientists consider Sauria to be the crown group of all reptiles. This means it includes most, if not all, modern reptiles and many extinct ones as well.

To understand how scientists define Sauria, we must look at how they group animals. Sauria sits within a larger group called Sauropsida. Sauropsida includes various "stem-reptiles" that are more closely related to reptiles than to mammals.

Scientists identify members of the Sauria clade by looking for specific shared traits. These traits are called synapomorphies. These are physical features that the common ancestor had, which were then passed down to its descendants. By looking for these specific markers, researchers can distinguish true saurians from older, more primitive reptiles.

These shared physical traits appear in many different parts of the body. In the head, or cephalad region, saurians often show a specific origin for their jaw muscles. They may also show a loss of certain teeth in the upper jaw, called the maxillary tooth row.

Other features include the position of the nostrils, or external nares, which are often close to the midline of the face. In the trunk, scientists look at the orientation of the sacral ribs and the structure of the ribs attached to the spine. Even the limbs provide clues. For example, the radius bone in the arm is often the same length as the ulna bone.

While some animals like birds or turtles have modified these traits, they are still seen as ancestral features of the group.

The way we define Sauria has changed significantly over time. In the 18th century, the name "Sauria" was used differently. Back then, it was a suborder that mostly described lizards and included crocodilians. Later, it was often used as a synonym for Squamata, which only covers lizards and snakes. This changed in the 1980s due to the work of Jacques Gauthier and his colleagues. Their research redefined Sauria to include the last common ancestor of archosaurs and lepidosaurs. This shifted the group from a small category of lizards to a massive branch of the tree of life.

Modern technology, especially genomic studies, has added even more detail to this history.

In 2012, a study led by Nicholas G. Crawford used genomic data to look at animal relationships. This study found evidence that turtles are the "sister group" to archosaurs. This means turtles are more closely related to birds and crocodiles than to lizards. This discovery helped place turtles firmly within the Sauria group. It moved them away from the older classification where they were thought to be related to a different group called parareptiles.

However, different scientific methods sometimes lead to different conclusions. Fossil evidence and genetic evidence do not always agree perfectly.

For example, in 2013, M.S. Lee analyzed the fossil record and found that a creature called Eunotosaurus was only distantly related to turtles. Lee placed Eunotosaurus in a different group called Parareptilia. In contrast, a 2015 study by Rainer Schoch and Hans-Dieter Sues used fossils to suggest that Eunotosaurus might actually be an early stem-turtle. Other researchers, such as Li et al. in 2018, have suggested that turtles might belong inside Diapsida but outside of Sauria. These different views show how much scientists are still learning.

Studying Sauria is important because it helps us map the history of life on Earth. It connects modern animals we see every day to ancient creatures from millions of years ago. By tracing these lineages, scientists can understand how complex body plans evolved. It shows how a single ancestor can eventually lead to the vast diversity of birds, crocodiles, and lizards. This work connects the study of genetics with the study of fossils. Together, these fields help us build a complete picture of how all living things are related.