| Megadolodus | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | † Litopterna |
| Family: | † Proterotheriidae |
| Subfamily: | † Megadolodinae |
| Genus: | † Megadolodus McKenna 1956 |
| Type species | |
| Megadolodus molariformis McKenna 1956 | |
| Species | |
| |
Megadolodus is an extinct genus of proterotheriid litopterns. [1]
The first fossils of Megadolodus were uncovered from the Villavieja Formation, in the fossil locality La Venta, in what is today Colombia, in terrains dated from the Middle Miocene, between 13.5 and 11.8 millions of years ago. The genus was described in 1956 after the holotype UCMP 39270, consisting in a left mandible preserving the fourth premolar, the first molar and roots from the second molar, and discovered during an expedition organized by the University of California and directed by Ruben A. Stirton. Those few remains led Malcolm McKenna, [2] who described them in his 1956 article, to believe they originated from a late surviving Didolodontidae, a family of primitive ungulates that went extinct during the end of the Eocene, 25 millions of years before the apparition of Megadolodus in the fossil record ; hence its genus name, meaning "large Didolodus ", a characteristic genus from this family. This classification supported the theory that the South American tropical zone acted as a refuge for primitive species during the Neogene. [3]
New remains of Megadolodus were only uncovered during the 1980s from the Honda Group, in the Magdalena River Valley of Colombia, including parts of the legs, mandibles, teeths, vertebrae, pelvis and ribs, permitting a better understanding of the general anatomy of the animal, and allowing to compare it with litopterns, resulting in its reclassification as an unusual Proterotheriidae. The discovery of a similar proterotheriid, Bounodus enigmaticus from Venezuela, confirmed that they belonged to a lineage of specialized litopterns from northern South America, classified in its own subfamily, the Megadolodinae. [4]
Megadolodus was a member of the Proterotheriidae, a family of small and medium-sized litopterns who produced in a few derived genera forms loosely evoking horses, such as the well known genera Thoatherium and Diadiaphorus . Megadolodus molariformis, the only known species from its genus, was itself characterized by its shorter and stronger limbs, its large tusk-like canines which sharpened each other, and a large hypocone on the third molar. The genus had only 10 to 11 thoracic vertebrae, and 5 lumbar vertebrae. [3]
Like some perissodactyls such as tapirs, Megadolodus had three toes on each limb, with the axis on the third toe, while the second and fourth toe were smaller and located in each side of the leg, without touching the ground. Weight estimates based on the comparison of its limbs with those of extant mammals suggest a weight between 30 and 200 kg, probably more precisely between 65 and 80 kg. [3] The fact that its body was not as slender than other proterotheriids, along with its canines and its bunodont molars similar to modern-day peccaries suggest that it was an animal similar in habits to modern Suidae, living in forested environments such as La Venta, and eating roots and fruits. [3]
Litopterna is an extinct order of fossil hoofed mammals from the Cenozoic era. The order is one of the five great orders of South American ungulates that were endemic to the continent, until the Great American Biotic Interchange brought new ungulate species. Like other endemic South American mammals, their relationship to other mammal groups had long been unclear, but recent genetic and proteomic evidence indicates that their closest living relatives are Perissodactyls including horses, rhinoceros, and tapirs, and that litopterns are closely related to notoungulates, another widespread group of South American ungulates.
Hapalops is an extinct genus of ground sloth from the Early to Late Miocene of Brazil, Bolivia, Colombia, and Argentina in South America.
La Venta is a fossil locality located in the modern departments of Tolima and Huila in Colombia. This site is one of the richest Neogene fossil assemblages in South America and represents the best-known Cenozoic fossil site outside of Argentina. It provides a glimpse of what life in the region was like before the main wave of the Great American Interchange.
Stirtonia is an extinct genus of New World monkeys from the Middle Miocene. Its remains have been found at the Konzentrat-Lagerstätte of La Venta in the Honda Group of Colombia. Two species have been described, S. victoriae and the type species S. tatacoensis. Synonyms are Homunculus tatacoensis, described by Ruben Arthur Stirton in 1951 and Kondous laventicus by Setoguchi in 1985. The genus is classified in Alouattini as an ancestor to the modern howler monkeys.
Proterotheriidae is an extinct family of fossil ungulates from the Cenozoic era that displays toe reduction. Despite resembling primitive, small horses, they were only distantly related to them, and instead belonged to the native South American ungulate order Litopterna.
Anachlysictis gracilis is an extinct carnivorous mammal belonging to the group Sparassodonta, which were metatherians that inhabited South America during the Cenozoic. Anachlysictis is the first record of such borhyaenoids in northern South America, and also the most primitive known member of the family Thylacosmilidae, a group of predators equipped with "saber teeth". It was also the only confirmed record of a thylacosmilid that did not belong to the genus Thylacosmilus until the official publication of Patagosmilus in 2010.
Xenastrapotherium is an extinct genus of astrapothere, a type of hoofed herbivorous mammal, native to South America, which lived in the Middle to Late Miocene period, typically during the Laventan stage. It is a member of the family Astrapotheriidae in the subfamily Uruguaytheriinae, large astrapotheres, equipped with a trunk-like nose and protruding teeth, similar to the elephants, but their tusks were the canine teeth, not the incisors. Xenastrapotherium was a genus widely distributed in northern South America, in contrast to other species of astrapotheres which lived in the area of the Southern Cone of the continent. It differed from other astrapotheres by having two lower incisors on each side of the jaw and the tusks have a pronounced longitudinal curvature, although their general shape and size are probably very similar to Astrapotherium, whose weight would be 900 to 1,500 kilograms, comparable to the current black rhino.
Colombophis is an extinct genus of snakes of the clade Alethinophidia, a group of "primitive" snakes. The genus was first recognized in the Villavieja Formation in the town of Los Mangos, part of the known fossil fauna of La Venta in the department of Huila (Colombia), in the middle Miocene. With the remains of a fossil snake was erected the species Colombophis portai in 1977, based on forty fragmentary vertebrae. These vertebrae are characterized by a low neural spine, and subdivided paradiapophysis and thin zygosphen. The vertebrae are medium to large, so the snake would measure about 1.77 metres long, similar in size to the current Boa constrictor.
Nuciruptor is an extinct genus of New World monkeys from the Middle Miocene. Its remains have been found at the Konzentrat-Lagerstätte of La Venta in the Honda Group of Colombia. The type species is N. rubricae.
Mohanamico is an extinct genus of New World monkeys from the Middle Miocene. Its remains have been found at the Konzentrat-Lagerstätte of La Venta in the Honda Group of Colombia. The type species is M. hershkovitzi. Due to the relatively few material found of Mohanamico, the placement of the genus is not certain and three possible families have been proposed by different authors, Callitrichidae, Pitheciidae or Aotidae.
Miocochilius is an extinct genus of small notoungulate mammals (typotheres) native to South America. The genus lived during the Middle Miocene epoch. The genus contains two described species, the type species M. anomopodus described in 1953 by Ruben Arthur Stirton and M. federicoi, described and included in the genus by Darin A. Croft.
Proterotherium is an extinct genus of litoptern mammal of the family Proterotheriidae that lived during the Late Miocene of Argentina and Chile. Fossils of this genus have been found in the Ituzaingó Formation of Argentina, and the Galera Formation of Chile.
Polymorphis is an extinct genus of litopterns belonging to the family Macraucheniidae. It lived during the Middle Eocene of Argentina.
Uruguayodon is an extinct genus of proterotheriid from the middle Pleistocene of Uruguay. It is known from the type and only species U. alius, named by Corona and colleagues in 2019 for dentaries and a partial postcrania from the Raigón Formation. Uruguayodon represents one of the latest occurrences of Proterotheriidae, with only Neolicaphrium representing other remains from the Pleistocene to possibly Holocene.
Anisolambda is an extinct genus of litoptern ungulate, belonging to the family Proterotheriidae. It lived from the Late Paleocene to the Middle Eocene in what is now South America.
Protheosodon is an extinct genus of litoptern ungulate, belonging to the family Proterotheriidae. It lived from the Late Oligocene to the Early Miocene, in what is today South America.
Prolicaphrium is an extinct genus of litoptern belonging to the family Proterotheriidae. It lived during the Early Miocene, in what is now [Argentina]].
Scirrotherium is an extinct genus of pampatheres, a family of herbivorous cingulates, related to the similar but smaller modern armadillos, and with the now extinct glyptodonts, well-known from their shell-like armor. Its scientific name is derived from the Greek prefix "skiros-", "cover", and the suffix "-therion, "beast", while the name of the type species, hondaensis, honors the town of Honda, in the Tolima Department of Colombia. Scirrotherium is one of several genera of xenarthrans found in the La Venta fauna, dated from the Middle Miocene.
Paranisolambda is an extinct genus of proterotheriid litopterns from the Early to Middle Eocene of Brazil. Fossils of Paranisolambda have been recovered from the Itaboraí Formation in the Brazilian state of Rio de Janeiro.
Villarroelia is an extinct genus of proterotheriid from the Middle Miocene of Colombia.
