| Xesmodon Temporal range: Middle-Late Eocene ~ | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | † Litopterna |
| Family: | † Proterotheriidae |
| Subfamily: | † Anisolambdinae |
| Genus: | † Xesmodon Berg, 1899 |
| Type species | |
| †Xesmodon langi (Roth, 1899) | |
| Species | |
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| Synonyms | |
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Xesmodon is an extinct genus of mammal. It lived from the Middle to the Late Eocene, in what is today South America.
Xesmodon was named by Carlos Berg in 1899. Its type species is Xesmodon langi, and a second species, Xesmodon prolixus, may also belong to the genus. [1] [2] Both species were named by Santiago Roth in 1899. The type and only known specimen of Xesmodon langi is a poorly preserved skull found at the locality Cañadón Colorado in Argentina. [3] The type and only known specimen of Xesmodon prolixus is a fragmentary mandible with two teeth found near Lago Musters in the Chubut Province of Argentina. [3] Both species are from the Mustersan South American land mammal age. [4]
Some researchers classify Xesmodon in Didolodontidae, [2] whereas others classify it in Anisolambdinae, a subfamily of Proterotheriidae. [5] Proterotheriidae is part of the order Litopterna, whereas didolodontids are considered condylarths, albeit likely to be closely related to litopterns.
This genus is known from partial cranial remains, permitting to partially reconstruct its appearance. The skull was rather long and low, and had particularly large orbites positioned near the middle of the skull. The nasal bones were elongated, while the frontal region was flat and table-like ;long and narrow postorbital apophyses separated from this region, to which jugal apophyses were not opposed. The zygomatic arch was rather thin. The upper molars of Xesmodon had a very strong independent hypocone.
In 1899, Santiago Roth named a new genus and species of mammal, Glyphodon langi, on the basis of a poorly preserved skull from Patagonia. He identified it as having litoptern affinities. In the same paper, he named the species Megacrodon prolixus. [6] However, the name Glyphodon had already been given to a snake by Albert Günther in 1858, so later the same year, Carlos Berg proposed the replacement name Xesmodon for Roth's genus. [7] In 1948, George Gaylord Simpson tentatively reclassified Megacrodon prolixus as a second species of Xesmodon. [1] Simpson was unsure whether Xesmodon was a didolodontid or a litoptern. [8] In 1983, Richard Cifelli assigned Xesmodon to Anisolambdinae. [5] In research by Miguel Soria published in 2001, [9] he classified Xesmodon in Didolodontidae. [2]
Litopterna is an extinct order of South American native ungulates that lived from the Paleocene to the end of the Pleistocene-early Holocene around 63 million-12,000 years ago, and were also present in Antarctica during the Eocene. They represent the second most diverse group of South American ungulates after Notoungulata. It is divided into nine families, with Proterotheriidae and Macraucheniidae being the most diverse and last surviving families.
Theosodon is an extinct genus of litoptern mammal from the Early to Middle Miocene of South America.
Cramauchenia is an extinct genus of litoptern South American ungulate. Cramauchenia was named by Florentino Ameghino. The name has no literal translation. Instead, it is an anagram of the name of a related genus Macrauchenia. This genus was initially discovered in the Sarmiento Formation in the Chubut Province, in Argentina, and later it was found in the Chichinales Formation in the Río Negro Province and the Cerro Bandera Formation in Neuquén, also in Argentina, in sediments assigned to the SALMA Colhuehuapian, as well as the Agua de la Piedra Formation in Mendoza, in sediments dated to the Deseadan. In 1981 Soria made C. insolita a junior synonym of C. normalis. A specimen of C. normalis was described in 2010 from Cabeza Blanca in the Sarmiento Formation, in sediments assigned to the Deseadan SALMA.
Proterotheriidae is an extinct family of litoptern ungulates known from the Oligocene-Late Pleistocene of South America. Members of the group were small-medium sized cursorial herbivores with brachydont teeth, with their toes showing progressive reduction, with later members of the group bearing weight on a single large toe similar to living horses.
Diplasiotherium is an extinct genus of litoptern belonging to the family Proterotheriidae, that lived between the late Miocene and the early Pliocene. The fossils of this animal have been found in Argentina, in the Monte Hermoso Formation.
Neolicaphrium is an extinct genus of ungulate mammal belonging to the extinct order Litopterna. This animal lived from the Late Pliocene (Chapadmalalan) to the Late Pleistocene (Lujanian) in southern South America, being the last survivor of the family Proterotheriidae.
Deuterotherium is an extinct genus of South American native ungulates, which lived during the Deseadan age of the Oligocene in what is now Argentina. Its type species is Deuterotherium distichum. It was named by Florentino Ameghino in 1895. The holotype of Deuterotherium distichum is a calcaneum. It was formerly identified as a proterotheriid litoptern. In 1999, Shockey argued Deuterotherium was certainly not a litoptern and interpreted it as a notohippid notoungulate. In research by Soria posthumously published in 2001, Soria considered Deuterotherium a nomen dubium.
Ernestokokenia is an extinct genus of mammal, belonging to the Didolodontidae. It lived during the Early Eocene and the Middle Eocene, and its fossils were discovered in South America.
Paulogervaisia is an extinct genus of mammal, belonging to the family Didolodontidae. Its fossilized remains have been found in South America.
Sparnotheriodontidae is an enigmatic extinct family of litopterns known primarily from teeth. Sparnotheriodontids are one of two South American native ungulate clades known to have reached Antarctica, the other being astrapotheres.
Asmithwoodwardia is an extinct genus of mammals, from the order Litopterna. It lived during the Late Paleocene and the Early Eocene, and its fossilized remains were found in South America.
Polymorphis is an extinct genus of litopterns belonging to the family Macraucheniidae. It lived during the Middle Eocene of Argentina.
Proadiantus(Ameghino, 1897) is an extinct genus of adianthid litoptern. It lived during the Late Oligocene, in what is today South America. It consists of only 1 species, Proadiantus excavatus.
Adiantoides is an extinct genus of herbivorous mammal, belonging to the order Litopterna. It lived during the Middle to Late Eocene, in South America.
Anisolambda is an extinct genus of litoptern. It lived from the Late Paleocene to the Middle Eocene in what is now Argentina.
Proectocion is an extinct genus of adianthid litoptern. It lived during the Early Eocene, in what is now South America.
Tetramerorhinus is an extinct genus of proterotheriid litoptern that lived during the Early and Middle Miocene in what is now Argentina and Peru.
Proacrodon is a dubious genus of extinct mammal from South America. Its type species is Proacrodon transformatus. The only known specimen, a lower premolar or molar, is now lost, and its affinities are unknown.
Pternoconius is an extinct genus of macraucheniid litoptern from the Late Oligocene and Early Miocene of Argentina. Fossils of this genus have been found in the Sarmiento Formation of Argentina.
Guilielmofloweria is an extinct genus of proterotheriid litoptern that lived from the Middle to Late Eocene of what is now Argentina. Fossils have been found in the Sarmiento Formation of Argentina.
