Hylonomus

This animal lived a long time ago.

It was small with a long tail. It had skin with hard scales.

It used small, sharp teeth to eat bugs. These bugs could be tiny insects.

Some fossils were found in old tree stumps. The trees fell over and became hollow. This small animal might have made a nest there. It might have also gotten stuck inside.

This animal is the special fossil of Nova Scotia.

It lived a very long time ago.

Hylonomus was a small animal from a long time ago.

Most were about 20 cm long. They had long tails. They may have looked like modern lizards.

These animals had small, sharp teeth. They likely ate small bugs like millipedes. Their bodies were covered in hard scales.

Hylonomus lived about 315 million years ago.

Scientists found many fossils in Nova Scotia, Canada. They found them inside old tree stumps. These stumps came from club mosses. Some think the animals made nests in the hollow stumps. Others think they went inside to hide from bad weather. Then they became trapped and died.

Scientists study these fossils to learn about history. Some think Hylonomus was the first reptile. Other studies say it was not quite a reptile. It was part of a group called amniotes. This group includes reptiles and mammals. In 2002, Hylonomus became the official fossil of Nova Scotia.

Hylonomus was a small animal that lived a very long time ago.

It lived during the Late Carboniferous period. Many scientists find this creature very important for history. Some early studies suggested it was the very first reptile.

Other studies from 2025 say it was not a true reptile. Instead, it was an early amniote. An amniote is a group that includes reptiles and mammals. This means it was a close relative to animals alive today.

This creature had a very specific way of living.

It was about 20 cm long including its long tail. Its body was covered in horny scales. It had small and sharp teeth for eating. Hylonomus likely ate small invertebrates like insects or millipedes. Its bones were slender and very lightweight. It had long and slim hands and feet. The arm and leg bones were the same length. It also had long bones in its neck.

We know about these animals because of fossils.

John William Dawson first described Hylonomus in 1860. He named the species Hylonomus lyelli. He named it to honor his teacher, Sir Charles Lyell. Dawson also named other species like H. aciedentatus and H. wymani. Later, scientists realized those were actually a different animal. In 1966, Robert L. Carroll changed how we group some species. He said H. latidens was the same as H. lyelli. He also moved H. multidens to a new group called Novascoticus.

Most fossils come from the Joggins Formation in Nova Scotia, Canada.

These fossils were found inside old club moss stumps. Scientists have two ideas about how this happened. One idea is that the animals used stumps for nests. Another idea is that they sought shelter from harsh weather. The stumps would rot and become hollow. Then the small animals would get trapped inside. They would eventually starve to death in the stumps. Fossil footprints in New Brunswick are also linked to them.

Learning about Hylonomus helps us see how life changed.

It lived about 315 million years ago. Other fossils like Archaeothyris were found in the same area. Those fossils lived about 6 million years later. In 2002, Hylonomus became the Provincial Fossil of Nova Scotia. This shows how much people value these old discoveries. It connects the tiny creatures of the past to our world. We can see how small changes lead to big groups of animals.

Hylonomus is an extinct genus of early amniote.

Amniotes are a group of animals that includes reptiles, birds, and mammals. This genus lived during the Bashkirian stage of the Late Carboniferous period. Scientists study Hylonomus to understand the early history of vertebrate life. It is a very important subject in the study of evolutionary history. For a long time, researchers have debated exactly where it fits on the tree of life.

Physically, Hylonomus had several unique features.

Most specimens were approximately 20 cm long, including their long tails. They likely looked similar to modern lizards. Their bodies were covered in horny scales. They possessed small, sharp teeth used to eat small invertebrates. These prey items likely included millipedes or early insects. Their skeletal structure was very lightweight. They had slender arm and leg bones of equal length. They also had long neck bones and slim hands and feet.

The anatomy of Hylonomus includes several specific biological details.

The mouth featured a narrow, tongue-shaped part in the roof. There was a deep groove on a specific bone in the skull. The back bones had a bumpy structure and varying heights. The skull also had a specific hole and a well-developed opening below the eye. Their feet had specific proportions. The fourth toe bone was short compared to the shin bone. The fifth toe bone was also short compared to the fourth toe bone. These traits define the physical makeup of the genus.

The history of Hylonomus involves many different scientific interpretations.

John William Dawson first described the genus in 1860. He named the species Hylonomus lyelli to honor his teacher, Sir Charles Lyell. Dawson originally identified other species, such as H. aciedentatus and H. wymani. However, later research reclassified these specimens. In 1966, Robert L. Carroll suggested that H. latidens was the same as H. lyelli. He also moved H. multidens into a different genus called Novascoticus. Eventually, other species were reclassified as Dendrerpeton acadianum.

Classification of Hylonomus has changed as technology has improved.

Early studies often called it a 'microsaur' or an ancestor to the crown group amniotes. Some 21st-century analyses suggested it was the earliest known reptile. However, a 2025 analysis used synchrotron data to revise its place in history. This new research placed Hylonomus outside of the amniote crown. This means it is less closely related to modern reptiles than mammals are. The analysis placed it after the Recumbirostra but before the Captorhinidae within Tetrapoda.

We learn about Hylonomus through the fossil record in North America.

Most fossils are found in the Joggins Formation in Nova Scotia, Canada. These fossils are often found inside the remains of fossilized club moss stumps. Scientists have two main theories about how this happened. One hypothesis is that Hylonomus used these hollow stumps to make nests. Another hypothesis is that they entered the stumps to find shelter from harsh weather. In this second scenario, the animals became trapped and starved to death. Fossilized footprints in New Brunswick are also attributed to this animal.

The significance of Hylonomus reaches into modern culture and geology.

These animals lived approximately 315 million years ago. In the same region of Nova Scotia, fossils of Archaeothyris and Petrolacosaurus exist. However, those fossils come from a higher stratum dated about 6 million years later. Because of its importance to the region, Hylonomus was named the Provincial Fossil of Nova Scotia in 2002. It serves as a vital link for understanding how early vertebrates transitioned through different stages of life.