| Megadolodus | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | † Litopterna |
| Family: | † Proterotheriidae |
| Genus: | † Megadolodus McKenna, 1956 |
| Species: | †M. molariformis |
| Binomial name | |
| †Megadolodus molariformis McKenna, 1956 | |
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] In 2024, partial mandible and teeth of Megadolodus are discovered from the Ipururo Formation of Peru. [5]
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 South American native ungulates that lived from the Paleocene to the end of the Pleistocene-early Holocene around 62.5 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.
Victorlemoinea is an extinct litoptern genus of the family Sparnotheriodontidae, that lived from the Early to Middle Eocene. Fossils of Victorlemoinea have been found in the Las Flores, Sarmiento and Koluel Kaike Formations of Argentina, the Itaboraí Formation of Brazil and La Meseta Formation, Antarctica.
Proterotheriidae is an extinct family of litoptern ungulates known from the Eocene-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.
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 rhinoceros.
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.
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.
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.
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. It lived from the Late Paleocene to the Middle Eocene in what is now Argentina.
Protheosodon is an extinct genus of proterotheriid litoptern. It lived from the Late Oligocene to the Early Miocene in what is now Argentina and Colombia.
Prolicaphrium is an extinct genus of proterotheriid litoptern that lived during the Early Miocene, in what is now Argentina. Fossils have been found in the Sarmiento Formation of Argentina.
Tetramerorhinus is an extinct genus of proterotheriid litoptern that lived during the Early and Middle Miocene in what is now Argentina and Peru.
Paramacrauchenia is an extinct genus of proterotheriid litopterns from the Early Miocene of what is now Argentina and Chile. Its fossils have been found in the Sarmiento and Santa Cruz Formations of Argentina and Chile.
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.
Magdalenabradys is an extinct genus of mylodontid ground sloths that lived during the Middle Miocene and Early Pliocene of what is now Colombia and Venezuela. Fossils have been found in the Villavieja Formation of the Honda Group in Colombia, and the Codore and Urumaco Formations of Venezuela.
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.
