''Requisia'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

litoptern Litopterna (from grc, λῑτή πτέρνα "smooth heel") 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 ...

from the

Early Paleocene The Danian is the oldest age or lowest stage of the Paleocene Epoch or Series, of the Paleogene Period or System, and of the Cenozoic Era or Erathem. The beginning of the Danian (and the end of the preceding Maastrichtian) is at the Cret ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

. Its fossilized remains were found in the

Salamanca Formation The Salamanca Formation is a geologic formation in the Golfo San Jorge Basin of central Patagonia that yields well-preserved, well-dated fossils from the early Paleocene. Studies of these fossils are providing new data on plant and animal diversit ...

in the

Chubut Province Chubut ( es, Provincia del Chubut, ; cy, Talaith Chubut) is a province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), the 46th parallel south (bordering Santa Cruz Province), the Andes ran ...

. It is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus, its only known species being ''Requisia vidmari''.

Description

It had a dental morphology quite similar to ''

Notonychops ''Notonychops'' is an extinct genus of mammal, belonging to the order Litopterna, that lived during the Middle to Late Paleocene in what is today South America. Description This genus is only known from a fragmentary mandible and maxilla, and i ...

'', but with more basal characters. The cuspid morphology, the type of wear and the crescent-shaped characters of the third upper molar indicates that ''Requisia vidmari'' had strong signs of solenodont characters, and is therefore considered as one of the basal representatives of the order Litopterna. ''Requisia'' is more basal than ''Notonychops'', but their morphological similarities could justify to include them in the same family, Notonychopidae, potentially alongside ''

Wainka ''Wainka'' is an extinct genus of South American mammal, belonging to the order Litopterna. It lived during the Middle Paleocene. Description This animal is only known for a few teeth. The upper molars were almost triangular in shape, elongated, ...

''. It is supposed that the adaptive radiation of South American

ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraff ...

s during the Paleocene was a fast phenomenon, which makes it difficult to find a satisfying phylogenetic model.BONAPARTE, J. F., MORALES, J. (1997). «Un primitivo Notonychopidae (Litopterna) del Paleoceno Inferior de Punta Peligro, Chubut, Argentina». ''Estudios Geol.'' 53: 263-274.

References

{{Taxonbar, from=Q10359610 Litopterns Paleocene mammals of South America Paleogene Argentina Fossils of Argentina Fossil taxa described in 1997 Prehistoric placental genera Golfo San Jorge Basin Taxa named by José Bonaparte Salamanca Formation