| Propachyrucos | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | † Notoungulata |
| Family: | † Hegetotheriidae |
| Genus: | † Propachyrucos Ameghino, 1897 |
| Species: | †P. smithwoodwardi |
| Binomial name | |
| †Propachyrucos smithwoodwardi Ameghino, 1897 | |
Propachyrucos is an extinct genus of late Oligocene hegetotheriid notoungulate. It is known from a few mandibular fragments from the Sarmiento Formation, Chubut Province, Argentina. [1]
Possibly similar to Prosotherium , but almost 20% smaller, more similar in size to Pachyrukhos and Paedotherium , and almost 30% larger than Tremacyllus . [1]
The molars had two internal folds separated by a further deep fold, like the Interatheriidae ; dental cementum was present, but to a lesser extent than in Interatherium . The lower teeth were flat on the outside and bilobed on the inside.[ citation needed ]
Propachyrucos was first described in 1897 by Florentino Ameghino, based on a right mandible fragment found in Oligocene terrains of the Sarmiento Formation in Argentina, initially believed by Ameghino to have been Cretaceous. The type species is Propachyrucos smithwoodwardi, but other species have been attributed to the genus, such as P. aequilatus, P. robustus, and P. ameghinorum, the latter species, described in 1945 by George Gaylord Simpson from fossils found in the Chubut Province, is known from a remarkably complete skeleton, permitting to reconstruct the animal appearance with high precision. However, recent researches tend to indicate that all the other species of Propachyrucos are in fact synonymous with the type species. [2]
Propachyrucos was a hegetothere, a group of notoungulates that evolved in isolation on the South American continent, giving rise to forms resembling hares and rabbits. Propachyrucos was a member of Pachyrukhinae, a subfamily of hegetotheres particularly similar to modern lagomorphs.
In a 1999 unpublished Ph.D. dissertation, the Propachyrucos species P. ameghinorum and P. simpsoni were synonymized with Prosotherium garzoni. This was supported by a 2019 reassessment as well as a number of other studies. As the most well preserved specimen of Propachyrucos was previously the nearly complete holotype of P. ameghinorum, Propachyrucos smithwoodwardi is now only known from a few mandibular fragments. The 2019 study recovers the features of P. ameghinorum as consistent with those of juvenile Prosotherium garzoni (although the holotype of P. ameghinorum was not directly examined). Despite this, until 2019, phylogenetic analyses regularly scored Propachyrucos for cranial and post-cranial characters, which are known only from the synonymized P. ameghinorum and P. simpsoni. [1]
Propachyrucos and its relatives were animals well suited to running and jumping. Body proportions similar to those of Propachyrucos's relatives can also be found in the Cainotheriidae, a group of artiodactyls from the Oligocene-Miocene of Europe. [1]
Rhynchippus is an extinct genus of notoungulate mammals from the Late Oligocene of South America. The genus was first described by Florentino Ameghino in 1897 and the type species is R. equinus, with lectotype MACN A 52–31. Fossils of Rhynchippus have been found in the Agua de la Piedra and Sarmiento Formations of Argentina, the Salla and Petaca Formations of Bolivia, the Tremembé Formation of Brazil, and the Moquegua Formation of Peru.
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.
The Deseadan age is a period of geologic time within the Oligocene epoch of the Paleogene to the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification of South America. It follows the Tinguirirican and precedes the Colhuehuapian age.
The Malargüe Group is a group of geologic formations of the Neuquén Basin of the Mendoza, Neuquén, Río Negro and La Pampa Provinces in northern Patagonia, Argentina. The formations of the Malargüe Group range in age between the middle Campanian to Deseadan, an Oligocene age of the SALMA classification, straddling the Cretaceous–Paleogene boundary, about 79 million to 30 million years in age. The group overlies the older Neuquén Group, separated by an unconformity dated to 79 Ma. The rocks of the Malargüe Group comprise both marine and continental deposits which are over 400 m (1312 ft) thick in total.
Hegetotherium is an extinct genus of mammals from the Early to Middle Miocene of South America. Fossils of this genus have been found in the Cerro Bandera, Cerro Boleadoras, Chichinales, Collón Curá, Santa Cruz and Sarmiento Formations of Argentina, the Nazareno Formation of Bolivia, and the Galera and Río Frías Formations of Chile.
Prohegetotherium is an extinct genus of hegetotheriid notoungulates from the Late Oligocene to Early Miocene of the Agua de la Piedra, Mariño & Sarmiento Formations of Argentina, the Petaca and Salla Formations of Bolivia, and Fray Bentos Formation of Uruguay.
The Agua de la Piedra Formation is a Late Oligocene geologic formation of the Malargüe Group that crops out in the southernmost Precordillera and northernmost Neuquén Basin in southern Mendoza Province, Argentina.
Paedotherium is an extinct, potentially paraphyletic genus of Notoungulate, belonging to the family Hegetotheriidae, composed of small-sized, rodent or lagomorph-like South American ungulates. Four species are unambiguously recognized, from the Late Miocene to the Pleistocene of Argentina, and from the late Miocene of Bolivia and Chile.
Prosotherium is an extinct genus of late Oligocene hegetotheriid notoungulate. It has been found in two Argentinian fossil formations, ie, the Sarmiento Formation in Chubut Province, and the Agua de la Piedra Formation in Mendoza Province.
Tremacyllus is an extinct genus of hegetotheriids. It lived from the Late Miocene to the Late Pleistocene and its fossilized remains were discovered in South America.
Proadinotherium is an extinct genus of toxodontid. It lived between the Late Oligocene and the Early Miocene in what is now South America.
Eohyrax is an extinct genus of Notoungulate, belonging to the suborder Typotheria. It lived during the Middle Eocene, and its remains were discovered in South America.
Asmodeus is an extinct genus of mammal, belonging to the order Notoungulata. It lived during the Late Oligocene, in what is today South America.
Ancylocoelus is an extinct genus of mammal, belonging to the order Notoungulata. It lived during the Late Oligocene, in what is today Argentina, in South America.
Argyrohyrax is an extinct genus of interatheriid notoungulate that lived during the Late Oligocene, of what is now Argentina and Bolivia.
Notopithecus is an extinct genus of Notoungulate, belonging to the suborder Typotheria. It lived from the Middle to the Late Eocene and its fossilized remains were discovered in South America.
Hegetotheriopsis is an extinct genus of hegetotheriid notoungulate. It lived from the Late Oligocene to the Early Miocene, and its fossilized remains are found in Argentina.
Sallatherium is an extinct genus of Notoungulate, belonging to the suborder Typotheria. It lived during the Late Oligocene, and its fossilized remains were discovered in South America.
The Sarmiento Formation, in older literature described as the Casamayor Formation, is a geological formation in Chubut Province, Argentina, in central Patagonia, which spans around 30 million years from the mid-Eocene to the early Miocene. It predominantly consists of pyroclastic deposits, which were deposited in a semi-arid environment. It is divided up into a number of members. The diverse fauna of the Sarmiento Formation, including a variety of birds, crocodilians, turtles and snakes, also includes many mammals such as South American native ungulates as well as armadillos, and caviomorph rodents.
Eopachyrucos is an extinct genus of interatheriid notoungulates that lived from the Middle Eocene to the Late Oligocene of Argentina and Uruguay. Fossils of this genus have been found in the Sarmiento Formation of Argentina and the Fray Bentos Formation of Uruguay.
