Three-toed sloth in the context of "Megatherioidea"

In tetrapods, cervical vertebrae (sg.: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sauropsid species, the cervical vertebrae bear cervical ribs. In lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae. The vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes. Most mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.

In humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a transverse foramen, an opening in each transverse process, through which the vertebral artery, vertebral veins, and inferior cervical ganglion pass. The remainder of this article focuses on human anatomy.

The brown-throated sloth (Bradypus variegatus) is a species of three-toed sloth found in the Neotropical realm of Central and South America.

It is the most common of the four species of three-toed sloth, and is found in the forests of South and Central America.

The northern maned sloth (Bradypus torquatus) is a three-toed sloth that is native to South America. It is one of four species of three-toed sloths belonging to the suborder Xenarthra and are placental mammals. They are endemic to the Atlantic coastal rainforest of southeastern and northeastern Brazil, located in the states of Espírito Santo, Rio de Janeiro and Bahia. Each of the individuals within the species are genetically distinct with different genetic makeup. The maned sloth is listed under Endangered (EN) according to the IUCN Red List and have a decreasing population trend.

The pale-throated sloth (Bradypus tridactylus), occasionally known as the ai (/ˈɑːi/), is a species of three-toed sloth that inhabits tropical rainforests in northern South America.

It is similar in appearance to, and often confused with, the brown-throated sloth, which has a much wider distribution. Genetic evidence has been interpreted to suggest the two species diverged only around 400,000 years ago, although the most recent evidence indicates the split was closer to 6 million years.

The southern maned sloth (Bradypus crinitus) is a three-toed sloth species.