| Thesodon Fossil range: Early Miocene | |
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| Scientific classification
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Thesodon | |
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Theosodon is an extinct genus of litoptern mammal from the early Miocene of South America.
Theosodon bore a superficial resemblance the modern guanaco, and was around 2 meters (6.6 ft) in length. It had a long neck and tapir-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.[1]
Theosodon had a full set of 44 teeth, and its lower mandible was very thin and large[2].
Description[]
Theosodon was long-legged with a long neck resembling modern llamas or guanacos. It was large for a litoptern, reaching up to 2 metres (6.6 ft) in length and weighing up to 170 kilograms (370 lb).
It had a long neck and tapir-like, three-toed feet, and like other litopterns and modern horses, tapirs and rhinos, it bore its weight on its middle toes.
Extraordinarily, rather than having nostrils at the front of its head, Theosodon had its nostrils on the top of its snout, halfway between the forehead and the tip of the snout, and its nostrils pointed upwards rather than forwards, possibly as an adaptation for browsing on prickly vegetation.
History[]
Theosodon has been known since the 19th century, and by 1910 seven species had been described within the genus, all from the early Miocene Santa Cruz Formation in Argentina. The name Theosodon means "god tooth". The first fossils were only dental remains, but it is unknown why this name was given. Though seven species had originally been described, the exact number of discovered species remains uncertain as it varies between different authors. There are either ten or seven species, and in 2014 Schmidt and Ferrero put forward that the genus needed a full taxonomic revision due to this issue.
"Theosodon" hystatus[]
In 1931, fossils found in the late Miocene Arroyo Chasicó Formation were assigned to the genus under the name Theosodon hystatus. This was questioned in 1995, and in 2014 it was moved to the genus Paranauchenia due to similarities to the species Paranauchenia denticulata. This move was supported by phylogenetic analysis that showed the two species formed monophyletic clade.
"Theosodon" arozquetai[]
In 2018 a new species of macraucheniid litoptern was described based on the partial remains of a skull and two metapodials. A phylogenetic analysis tentatively linked the species to Theosodon as a sister clade and it was named Theosodon arozquetai pending revision. Its body mass was estimated to be somewhere from 80.8 to 116.2 kilograms (178 to 256 lb). It dated to the middle Miocene, about 13 million years ago, somewhat later than most other Theosodon species.
Classification[]
References[]
- ^ Palmer, D., ed (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 247. ISBN 1-84028-152-9.
- ^ [1]
