Temporal range: Early Eocene (Casamayoran-Mustersan)
Thomashuxleya is an extinct genus of notoungulate mammal, named after famous 19th-century biologist Thomas Huxley.
A biologist is a scientist who has specialized knowledge in the field of biology, the scientific study of life. Biologists involved in fundamental research attempt to explore and further explain the underlying mechanisms that govern the functioning of living matter. Biologists involved in applied research attempt to develop or improve more specific processes and understanding, in fields such as medicine and industry.
Thomashuxleya was about 1.3 metres (4.3 ft) in length and weighted an estimated 113 kilograms (249 lb), with a heavy body and strong limbs. Its large skull had 44 teeth in its jaws, including large tusks which may have been used to dig around in earth. It had four toes on each foot, and probably walked somewhat like a modern peccary. It was a relatively generalised animal, not specialised for any particular way of life. There's an almost complete skeleton of this animal in exhibition in the American Museum of Natural History. This skeleton was discovered during the Scarrit expedition to Patagonia, Argentina, that was led by the paleontologist George Gaylord Simpson. Fossils of Thomashuxleya have been found in the Sarmiento and Casamayor Formations of Argentina.
The skull is a bony structure that forms the head in vertebrates. It supports the structures of the face and provides a protective cavity for the brain. The skull is composed of two parts: the cranium and the mandible. In the human, these two parts are the neurocranium and the viscerocranium or facial skeleton that includes the mandible as its largest bone. The skull forms the anterior most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, and mouth. In humans these sensory structures are part of the facial skeleton.
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of most animals.
A peccary is a medium-sized pig-like hoofed mammal of the family Tayassuidae. They are found throughout Central and South America and in the southwestern area of North America. Peccaries usually measure between 90 and 130 cm in length, and a full-grown adult usually weighs about 20 to 40 kg.
Steller's sea cow is an extinct sirenian discovered by Europeans in 1741. At that time, it was found only around the Commander Islands in the Bering Sea between Alaska and Russia; its range was more extensive during the Pleistocene epoch, and it is possible that the animal and humans previously interacted. Some 18th-century adults would have reached weights of 8–10 t and lengths up to 9 m (30 ft).
Cynognathus is an extinct genus of large-bodied cynodont therapsids that lived in the Middle Triassic. It is known from a single species, Cynognathus crateronotus. Cynognathus was a 1.2-metre long predator closely related to mammals and had a southern hemispheric distribution. Fossils have so far been recovered from South Africa, Argentina, Antarctica, and Namibia.
Toxodon is an extinct genus of South American mammals from the Late Miocene to Middle Holocene epochs. It is a member of Notoungulata, one of several now extinct orders of hoofed mammals indigenous to South America. It was among the largest and last members of its order, and was probably the most common large-hoofed South American mammal of its time.
Toxodonta or Toxodontia is a suborder of the meridiungulate order Notoungulata. Most of the members of the five included families, including the largest notoungulates, share several dental, auditory and tarsal specializations. The group is named after Toxodon, the first example of the group to be discovered by science.
Thylacosmilus is an extinct genus of saber-toothed metatherian that inhabited South America from the Late Miocene to Pliocene epochs. Though Thylacosmilus is one of several predatory mammal genera typically called "saber-toothed cats", it was not a felid placentalian, like the well-known North American Smilodon, but a sparassodont, a group closely related to marsupials, and only superficially resembled other saber-toothed mammals due to convergent evolution. A 2005 study found that the bite forces of Thylacosmilus and Smilodon were low, which indicates the killing-techniques of saber-toothed animals differed from those of extant species. Remains of Thylacosmilus have been found primarily in Catamarca, Entre Ríos, and La Pampa Provinces in northern Argentina.
Macrauchenia was a long-necked and long-limbed, three-toed South American ungulate, typifying the order Litopterna. The oldest fossils date to around seven million years ago, and M. patachonica disappears from the fossil record during the late Pleistocene, around 20,000-10,000 years ago. M. patachonica was the best known member of the family Macraucheniidae, and is known only from fossil finds in South America, primarily from the Luján Formation in Argentina. The type specimen was discovered by Charles Darwin during the voyage of the Beagle. In life, Macrauchenia resembled a humpless camel with a short trunk, though it is not closely related to either camels or proboscideans.
Peltephilus, the horned armadillo, is an extinct genus of dog-sized, armadillo xenarthran mammals which first inhabited Argentina during the Oligocene epoch, and became extinct in the Miocene epoch. Notably, the scutes on its head were so developed that they formed horns protecting its eyes. Aside from the horned gophers of North America, it is the only known fossorial horned mammal.
Lycaenops ("wolf-face") is a genus of carnivorous therapsids. It lived during the late mid-Permian to the early Late Permian, about 270.6-251 mya, in what is now South Africa.
Planetetherium is an extinct genus of herbivorous gliding mammal endemic to North America during the Paleogene living from 56.8—55.4 mya, existing for approximately.
Prosqualodon is an extinct genus of Early to Middle Miocene cetacean from Argentina, Australia, New Zealand and Venezuela.
Chriacus is an extinct genus of prehistoric mammal which lived in North America around 63 million years ago. There are 9 valid species currently recognized.
Diadiaphorus is an extinct genus of litoptern mammal from the Miocene of Argentina and Bolivia, South America.
Notostylops is a genus of extinct South American ungulate from the Eocene Argentina. Fossils of the genus have been found in the Sarmiento, Casamayor, Andesitas Huancache and Koluel Kaike Formations.
Protypotherium is an extinct genus of notoungulate mammals native to South America during the Miocene epoch. A number of closely related animals date back further, to the Paleocene. Fossils of Protypotherium have been found in the Deseadan Fray Bentos Formation of Uruguay, Muyu Huasi Formation of Bolivia, Cura-Mallín and Río Frías Formations of Chile and Santa Cruz, Salicas, Ituzaingó, Cerro Bandera, Chichinales, Sarmiento and Collón Curá Formations of Argentina.
Pachyrukhos is an extinct genus of mammals from the Late Oligocene to Middle Miocene of Argentina and Chile, South America.
Scarrittia is an extinct genus of hoofed mammal of the family Leontiniidae, native to South America during the Late Oligocene epoch.
Megacerops is an extinct genus of the prehistoric odd-toed ungulate family Brontotheriidae, an extinct group of rhinoceros-like browsers related to horses. It was endemic to North America during the Late Eocene epoch, existing for approximately.
Several mammals are known from the Mesozoic of Madagascar. The Bathonian Ambondro, known from a piece of jaw with three teeth, is the earliest known mammal with molars showing the modern, tribosphenic pattern that is characteristic of marsupial and placental mammals. Interpretations of its affinities have differed; one proposal places it in a group known as Australosphenida with other Mesozoic tribosphenic mammals from the southern continents (Gondwana) as well as the monotremes, while others favor closer affinities with northern (Laurasian) tribosphenic mammals or specifically with placentals. At least five species are known from the Maastrichtian, including a yet undescribed species known from a nearly complete skeleton that may represent a completely new group of mammals. The gondwanathere Lavanify, known from two teeth, is most closely related to other gondwanatheres found in India and Argentina. Two other teeth may represent another gondwanathere or a different kind of mammal. One molar fragment is one of the few known remains of a multituberculate mammal from Gondwana and another has been interpreted as either a marsupial or a placental.
Astrapotherium is an extinct genus of South American mammal which vaguely resembled a cross between a small elephant, and a very large tapir. This peculiar-looking animal was unrelated to modern elephants, and was, instead, related to other extinct South American ungulates. The beast lived in the Early to Middle Miocene. Fossil remains of the type species A. magnus have been found in the Santa Cruz Formation in Argentina. Other fossils have been found in the Deseado, Sarmiento and Aisol Formations of Argentina and Chile.
Necrolestes is an extinct genus of non-therian mammals, which lived during the Early Miocene in what is now Argentine Patagonia. It contains two species, N. patagonensis and N. mirabilis, and is the most recent known genus of dryolestoid. The type species N. patagonensis was named by Florentino Ameghino in 1891 based on remains found by his brother, Carlos Ameghino in Patagonia. Fossils of Necrolestes have been found in the Sarmiento and Santa Cruz Formations.
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