Tuatara

The tuatara is a special reptile.

It lives in New Zealand. It has bumps on its back.

These bumps are bigger on males.

This animal is not a lizard. It is the only one left from its own big group. Long ago, many other kinds lived in the world.

It has a very cool mouth. It has a second row of teeth on the roof of its mouth. This helps it eat.

Its skin can be green or brown. It sheds its skin every year.

Some animals in New Zealand are in danger. People work hard to keep the tuatara safe.

The tuatara is a special reptile from New Zealand.

It looks like a lizard. However, it is not a lizard. It is the only living member of a group called Rhynchocephalia.

This group was very large a long time ago.

Tuatara have many unique parts. They have a spiny crest on their backs. This crest is larger on males.

Their mouths are also very special. They have a second row of teeth on the roof of their mouths. This is called palatal dentition. When they bite, the lower jaw slides between the two upper rows. This helps them chew through hard things like bone.

Their eyes are very good. They have a third eyelid to protect them. They can see well in the light and the dark.

Tuatara face many dangers today. New animals like rats can hurt them. They also lose the places where they live. People now work to protect them. In 2005, some were moved to a safe place called Zealandia. In 2008, a nest was found there. This was a big win for the tuatara.

The tuatara is a very special reptile from New Zealand.

While it looks like a lizard, it is actually something much more unique. It is the only living member of an ancient group called Rhynchocephalia. This group was once very large and lived all over the world. Today, the tuatara is the only survivor of this entire lineage. Because it has stayed so similar to its ancestors, people sometimes call it a "living fossil."

This reptile has a very interesting way of eating. Most lizards have teeth attached to the inside of their jaws. However, tuatara have teeth that are fused to the very top of their jawbone. They also have a second row of teeth on the roof of their mouths. This is called palatal dentition. When they bite down, their lower jaw slides between these two upper rows. This special movement helps them shear through hard things like bone or shells.

Scientists have spent a long time studying how to name and group the tuatara. In 1831, the British Museum received a skull and thought it was a lizard. A man named John Edward Gray gave it the name *Sphenodon*. This name comes from Greek words meaning "wedge" and "tooth." Later, in 1867, Albert C. L. G. Günther realized the animal was not a lizard. He saw features that were more like birds or crocodiles. He proposed the order Rhynchocephalia, which means "beak head."

There are many specific facts about how a tuatara lives and grows. Adult males can grow up to 36 inches long and weigh up to 1 kilogram.

They are greenish-brown or grey, and they shed their skin at least once a year. Their eyes are very advanced and can focus independently. They even have a third eyelid, called a nictitating membrane, to protect them. They have special cells that help them see well in both bright light and the dark.

Today, the tuatara faces some hard jobs to stay safe. They are threatened by habitat loss and predators like the Polynesian rat. For a long time, they only lived on 32 small islands. However, people have worked hard to help them move back to the mainland. In 2005, some were released into a protected area called Zealandia. In 2008, workers found a nest there with a tiny hatchling inside. This was a huge success because it was the first time they bred on the North Island in over 200 years.

The tuatara (*Sphenodon punctatus*) is a unique reptile found only in New Zealand.

While it looks like a lizard, it is actually the only living member of a distinct lineage. This lineage belongs to the order Rhynchocephalia. The name tuatara comes from the Māori language and means "peaks on the back." This name describes the spiny crest found on their bodies. The tuatara is a vital subject for scientists studying reptile evolution.

The tuatara has a very specialized way of eating. Its teeth are acrodont, meaning they are attached to the very top of the jawbone. Unlike most lizards, which have pleurodont teeth attached to the inside of the jaw, tuatara teeth are fused to the bone. They also have palatal dentition, which is a second row of teeth on the roof of the mouth. When the animal bites, the lower jaw slides forward between these two upper rows. This specific mechanism allows the jaws to shear through hard materials like bone or chitin.

The anatomy of the tuatara includes several unusual skeletal features. They possess gastralia, which are bony plates located in the belly area. Their skull also has a completely fused temporal bar at the back. This bar closes the lower temporal fenestra, an opening behind the eye socket. This structure is thought to stabilize the skull while the animal is biting. Most lizards have an open structure here, but the tuatara's fused bar is a derived characteristic of the Sphenodontinae group.

History shows how scientists have worked to correctly classify this animal. In 1831, the British Museum received a skull and initially classified it as a lizard. John Edward Gray named the genus *Sphenodon*, which comes from the Greek words for "wedge" and "tooth." In 1867, Albert C. L. G. Günther noticed features similar to birds and crocodiles. He proposed the order Rhynchocephalia, meaning "beak head." This corrected the earlier mistake of calling them lizards.

The Rhynchocephalia order was once incredibly diverse throughout the world. They first appeared in the fossil record during the Middle Triassic, about 244 to 241.5 million years ago. During the Jurassic period, they were the dominant group of small reptiles globally. This group included various forms, such as the aquatic pleurosaurs and herbivorous eilenodontines. The group eventually declined during the Cretaceous period. Their youngest records outside of New Zealand date back to the Paleocene.

Physical measurements and traits vary between males and females. Adult males can reach 36 inches in length and weigh up to 1 kilogram. Females are generally smaller. The tuatara is sexually dimorphic, meaning males and females have different physical appearances. Males often have a larger, spiny crest made of soft skin folds. Their skin can be greenish-brown or grey and changes over their lifetime. They also have advanced eyes with a nictitating membrane, or third eyelid.

Conservation efforts are essential for the survival of the tuatara. They are threatened by habitat loss and introduced predators like the Polynesian rat. For a long time, they lived only on 32 offshore islands. In 2005, a group was released into the Zealandia sanctuary on the North Island. In 2008, a nest was found during maintenance work. A hatchling was discovered the following autumn. This was the first successful wild breeding on the North Island in over 200 years.