Artiodactyla

Some animals walk on an even number of toes.

They use two toes to carry their weight. This group includes pigs, deer, and giraffes.

Many of them eat plants for food. They have special stomachs to help them.

Even whales and dolphins are part of this group. They are very close to hippos. These animals are very important to people.

Some animals walk on an even number of toes. These animals are called artiodactyls. They carry their weight on two toes. This is different from other animals that walk on an odd number of toes.

Many artiodactyls eat plants. They have special stomach chambers to help them digest food. This group includes many animals we know. You might see pigs, deer, or giraffes.

Other members are camels, llamas, and sheep. Some, like pigs, eat both plants and meat.

Scientists found a big surprise. Whales and dolphins are also part of this group. They are most closely related to hippos.

Researchers used molecular biology to find this out. This is a way to study DNA. DNA is the code inside living things. By looking at this code, they saw the link. Even though whales live in the ocean, they share a common ancestor with land animals.

Artiodactyls are a large group of mammals that we often call even-toed ungulates.

These animals are special because they carry their weight on an even number of toes. Usually, they use their third and fourth toes to walk. These toes often grow into a hard hoof. This is different from perissodactyls, which walk on an odd number of toes. Many artiodactyls are herbivores that eat plants. They have special stomach chambers to help them digest plant cellulose. This way of eating helps them get energy from tough plants. Some members, like pigs, are omnivores and eat both plants and meat.

How these animals live and eat can vary a lot.

Most land-based artiodactyls are herbivores, such as cattle, sheep, and goats. Others, like the camel or the llama, live in different environments. Some animals in this group are even more surprising. Scientists found that whales, dolphins, and porpoises belong to this branch too.

These ocean animals are called cetaceans. They are most closely related to hippopotamuses. Because they are so different, some scientists use a new name, Cetartiodactyla, to include both the land and sea animals. This name helps show they all share a common history.

We can look back in time to see where they began.

The oldest fossils of even-toed ungulates are about 53 million years old. These fossils come from the early Eocene period. They were found in Europe, Asia, and North America at the same time. This makes it hard to know exactly where they first started. The very first artiodactyls belonged to a family called Diacodexeidae.

One famous member was called Diacodexis. These were small animals, sometimes only as big as a hare. They had slim bodies, long tails, and legs that were longer in the back than the front.

Many different kinds of artiodactyls have lived throughout history.

Some were very large, like the Entelodonts. These animals lived from the middle Eocene to the early Miocene. They had stocky bodies and massive heads with bony bumps on their jaws. Another group called Anthracotheres lived from the middle Eocene to the Pliocene.

These animals were pig-like and are thought to be the ancestors of modern hippos. Hippos themselves appeared later, in the late Miocene. They live in Africa and Asia but never lived in the Americas. Other groups, like the Merycoidodontidae, were camels that lived in North America until about 10,000 years ago.

Learning about these animals involves much more than just looking at bones.

In the 1990s, researchers began using molecular biology to study them. This means they look at the DNA, or the genetic code, inside living things. By comparing DNA, scientists proved that whales are related to even-toed ungulates.

They also found fossils in Pakistan that helped tell the story. These fossils, like Pakicetus, were about 48 million years old. These ancient whales had ankle bones that looked just like the ones in land animals. This discovery helped prove how a land animal could eventually become a whale.

Artiodactyla is a large order of placental mammals known as even-toed ungulates.

These animals are defined by how they carry their weight. They bear weight equally on an even number of toes, usually two. Specifically, they use the third and fourth toes, which often form a hard hoof. This distinguishes them from perissodactyls, which bear weight on an odd number of toes.

This group includes many animals that are vital to human culture and economy. They range from small deer to massive giraffes and camels.

One of the most important features of many artiodactyls is how they digest food. Most members of this order are herbivores that eat plants. To process tough plant cellulose, they use one or more specialized stomach chambers. This process is more efficient than the intestinal digestion used by perissodactyls. However, not all artiodactyls follow this rule. The Suina, which includes pigs, are omnivores that eat both plants and meat.

Cetaceans, such as whales and dolphins, are entirely carnivorous.

Modern science has revealed a surprising connection within this group.

Molecular biology has shown that cetaceans are part of the artiodactyl branch. Specifically, whales and dolphins are most closely related to hippopotamuses. Because of this, some taxonomists use the name Cetartiodactyla to include both groups. This ensures the group is monophyletic, meaning it includes a common ancestor and all its descendants. Other researchers use the term "even-toed ungulates" to refer only to the land-dwelling species.

The evolutionary history of artiodactyls began in the early Eocene, about 53 million years ago.

Fossils from this era appeared almost at once in Europe, Asia, and North America. This makes it difficult for scientists to pinpoint their exact place of origin. The earliest known family is Diacodexeidae. Their most famous member was Diacodexis. These were small, slim animals, sometimes only the size of a hare. They had long tails and hind legs that were longer than their front legs.

Many extinct families once roamed the Earth.

The Entelodontidae were stocky animals with massive heads and bony bumps on their lower jaws. They lived from the middle Eocene to the early Miocene in Eurasia and North America. Another group, the Anthracotheriidae, had a pig-like build and lived from the middle Eocene to the Pliocene. These animals are thought to be the ancestors of modern hippopotamuses. Hippos appeared later, in the late Miocene, and live in Africa and Asia today.

Other groups show how these animals spread across the globe. The Merycoidodontidae were a diverse group of North American camels. They lived in North America until they went extinct around 10,000 years ago.

Terrestrial artiodactyls only reached South America in the Pliocene. This happened after the Isthmus of Panama formed about three million years ago. Because of this late arrival, South America has fewer artiodactyl families than other continents. Australia has no native terrestrial species, and Antarctica has no terrestrial mammals at all.

Scientists confirmed these relationships using molecular biology.

By sequencing DNA and RNA, researchers compared genetic material between species. In 1994, scientists like Dan Graur and Desmond Higgins used these methods to link cetaceans to artiodactyls. Fossil evidence from Pakistan also provided crucial clues.

Fossils of Pakicetus, an ancient whale from 48 million years ago, showed a specific ankle bone structure. This double-rolled joint surface is a trait shared with even-toed ungulates. This physical link proves that whales evolved from land-dwelling ancestors.