Snake

Snakes are long animals with no legs.

They have scales that overlap on their skin.

Some snakes have special bones in their heads. This helps them swallow big food.

Most snakes do not have venom.

Some snakes use venom to catch food. Others squeeze their prey to catch it.

Many snakes live on almost every land.

Some snakes even live in the sea. You can find them in many places. They are very different from lizards.

Snakes are amazing animals to see.

Snakes are long reptiles with no legs.

They are covered in scales that overlap. Snakes live on almost every continent. You can find them in the sea, too.

Many snakes have a special skull. It has extra joints to help them swallow. This lets them eat prey much larger than their heads.

Most snakes do not have venom. Some snakes use venom to kill prey. Other snakes use constriction, which means they squeeze their food.

Snakes evolved from lizards. Some snakes still have tiny parts from their ancestors. We call these vestigial parts. For example, pythons have tiny claws called anal spurs.

These parts are left over from when their ancestors had legs. Most snakes have a very long chest area. This is why they have so many ribs. There are more than 4,170 species of snakes in the world today. They can be tiny or very long.

Snakes are amazing reptiles that belong to a group called Serpentes.

They are known for their long bodies and lack of limbs. These animals are ectothermic, which means they rely on the world around them to stay warm. Most snakes are covered in overlapping scales.

They are found on every continent except for Antarctica. You can find them on many small islands and even in the sea.

Sea snakes live throughout the Indian and Pacific oceans.

A snake's body is built in a very special way.

Because their bodies are so narrow, their internal organs are arranged differently. Instead of being side by side, organs like the kidneys sit one in front of the other. Most snakes also only have one working lung. Their skulls have many extra joints, a trait called cranial kinesis. This allows them to swallow prey that is much larger than their own heads.

Some snakes kill prey by squeezing, which is called constriction. Others use venom to subdue their food.

Scientists believe snakes evolved from lizards.

This change likely happened during the Jurassic period. The earliest known fossils of true snakes are about 112 to 94 million years old. These fossils belong to a group called marine simoliophids. Many modern snake groups appeared later during the Paleocene epoch. This was about 66 to 56 million years ago. This time followed a major extinction event that changed life on Earth. The diversity of snakes grew as the world changed.

There is a huge variety of snakes in our world today.

Experts recognize about 30 different families of snakes. These families include more than 520 genera and over 4,170 species. Snakes can be very small, like the tiny Barbados threadsnake.

Other snakes are huge, such as the reticulated python. Some species, like vipers and elapids, appeared in North America during the Miocene. This was a time when grasslands began to spread across the land.

It is easy to confuse snakes with some types of lizards. Some lizards have evolved to have long bodies without legs. This is called convergent evolution. However, you can tell them apart by looking closely. Most legless lizards have eyelids and external ears. Snakes do not have these features.

Even though they look similar, their bodies work in different ways. Snakes have a very long chest area with many ribs. This makes their skeleton very different from most other reptiles.

Snakes are elongated, limbless reptiles belonging to the suborder Serpentes. As members of the clade Squamata, they are ectothermic vertebrates, meaning they rely on external heat sources to regulate their body temperature.

Most snakes are covered in overlapping scales, a characteristic shared with many other reptiles. They are found on every continent except Antarctica. They inhabit most small land masses, though they are absent from large islands like Ireland, Iceland, and Greenland.

Sea snakes are also widespread throughout the Indian and Pacific oceans.

The internal anatomy of a snake is highly specialized to accommodate its narrow body. In most vertebrates, paired organs like the kidneys are positioned side by side. In snakes, these organs appear one in front of the other.

Furthermore, most species possess only one functional lung. A major anatomical advantage is cranial kinesis, which refers to the many joints in the skull. This flexibility allows snakes to swallow prey that is much larger than their own heads.

This mechanism is vital for their survival as predators.

Snake skeletons differ significantly from those of their lizard ancestors. This change is driven by the evolution of Hox genes, which control limb morphogenesis, or the development of limbs. In snakes, the expression of genes responsible for the thorax, or chest area, became dominant. As a result, most of a snake's skeleton is an extremely extended thorax.

While most reptiles have distinct neck, chest, lower back, and tail sections, snakes have a highly reduced number of lumbar and pelvic vertebrae. They typically possess only 2 to 10 lumbar or pelvic vertebrae. Ribs are found exclusively on the thoracic vertebrae. Some primitive groups, like boas and pythons, still retain vestigial hind limbs known as anal spurs.

Taxonomically, modern snakes are divided into two main infraorders: Alethinophidia and Scolecophidia. This classification is based on morphological characteristics and similarities in mitochondrial DNA sequences.

Alethinophidia is a large group that includes various families like Colubridae, Viperidae, and Elapidae. Scolecophidia consists of smaller, often blind snakes. Within the Alethinophidia, some scientists further divide the group into Henophidia and Caenophidia. This complex system helps scientists organize the immense variety of species found globally.

The evolutionary history of snakes is linked to lizards. Genomic analysis and comparative anatomy confirm that snakes descended from lizards, perhaps during the Jurassic period. The fossil record is often difficult to study because snake skeletons are small and fragile. However, the earliest known true snake fossils, such as the marine simoliophid *Haasiophis terrasanctus*, date to the Late Cretaceous, between 112 and 94 million years ago. The modern diversity of snakes expanded during the Paleocene epoch, roughly 66 to 56 million years ago. This followed the Cretaceous–Paleogene extinction event.

Today, there is incredible biological diversity among snakes. Scientists recognize approximately 30 families, which include about 520 genera and more than 4,170 species.

Sizes vary drastically across the group. The Barbados threadsnake is among the tiniest, while the reticulated python is among the largest. Most species are nonvenomous and use constriction to kill prey.

Venomous species use toxins to subdue prey, though some venoms are potent enough to cause serious injury to humans. This diversity allows snakes to occupy many different ecological niches.

It is important to distinguish snakes from legless lizards. Some lizards have independently evolved long, limb-less bodies through a process called convergent evolution. This means they developed similar traits to snakes even though they are not closely related. You can often tell them apart by looking for specific features. Many common groups of legless lizards possess eyelids and external ears, whereas snakes lack these structures. By studying these physical differences, biologists can accurately classify the vast array of creeping, crawling reptiles in our world.