Theosodon is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of litoptern mammal from the early Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 of South America.

Theosodon bore a superficial resemblance the modern guanaco, and was around 2 metres (6.6 ft) in length. It had a long neck and tapir

Tapir

A Tapir is a large browsing mammal, similar in shape to a pig, with a short, prehensile snout. Tapirs inhabit jungle and forest regions of South America, Central America, and Southeast Asia. There are four species of Tapirs: the Brazilian Tapir, the Malayan Tapir, Baird's Tapir and the Mountain...

-like, three-toed feet. Judging from the position of its nostrils, Theosodon had a short trunk, though shorter than its other relatives, such as Macrauchenia

Macrauchenia

Macrauchenia was a long-necked and long-limbed, three-toed South American ungulate mammal, typifying the order Litopterna. The oldest fossils date back to around 7 million years ago, and M...

.

Theosodon had a full set of 44 teeth, and its lower mandible

Mandible

The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

was very thin and large.