Simian

The simians, also called anthropoids or higher primates, are a group of primates known as the infraorder Simiiformes. This large family includes all animals we commonly call monkeys and apes.

Within this group are two main branches: the Platyrrhini, known as New World monkeys, and the Catarrhini, which includes Old World monkeys and apes, the latter of which includes humans.

Simians are closely related to tarsiers, and together they make up a group called haplorhines. These animals began to diversify about 60 million years ago during the Cenozoic era.

Around 40 million years ago, some simians traveled to South America and evolved into the New World monkeys. The other simians, known as catarrhines, later split into two groups: the Cercopithecidae family and the apes, which include humans.

These fascinating creatures have played an important role in understanding evolution and human origins. By studying simians, scientists can learn more about how humans and other primates are connected and how life has changed over millions of years.

Taxonomy

Simians, also called anthropoids, include monkeys and apes. They belong to a group named haplorhines, which also has tarsiers. Older classifications put simians under Anthropoidea, but today we know they are part of the suborder Haplorhini.

Both Simiiformes and Anthropoidea are names used for simians. Some scientists like Simiiformes because it fits better with naming rules for infraorders. There were also simian species that lived millions of years ago, helping us learn more about these primates.

Main article: Anthropoidea
Main articles: Primatology, Paleoanthropology

Evolution

Scientists think that monkeys and apes first appeared in Africa. Some believe they may have started in Asia and traveled to Africa on natural rafts during the Eocene period. Early fossils of these animals have been found in northern Africa, in places like Algeria, Libya, and Egypt.

Around 40 million years ago, New World monkeys separated from the rest of the simian line. This left the Old World monkeys and apes to keep evolving together. About 25 million years ago, the Old World monkeys split from the apes, showing they are more closely related to apes than to New World monkeys.

Main articles: Cercopithecidae

Classification

The simians are a group of primates that include all monkeys and apes. They belong to the infraorder Simiiformes, which is part of the suborder Haplorhini. This group includes tarsiers and monkeys, with simians being closely related to tarsiers.

Simians are divided into two main groups: the parvorder Platyrrhini, which are New World monkeys, and the parvorder Catarrhini, which includes Old World monkeys and apes. New World monkeys live in South and Central America and include families like marmosets, capuchins, and spider monkeys. Old World monkeys and apes live mainly in Africa and Asia and include gibbons and great apes, such as chimpanzees, gorillas, and humans.

Biological key-features

Simians, also known as anthropoids, have some special traits. They have big brains, eyes that face forward for better sight, and they can see colors well. These primates also have jawbones that are joined together, and their females usually have one uterus.

One difference between New World simians and Old World simians is their nose shape and teeth. New World simians have broader noses with nostrils that face forward and more teeth. Old World simians have narrower noses with nostrils that face downward and fewer teeth.