''Simpsonotus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of notoungulate

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

s in the family

Henricosborniidae Henricosborniidae is a family of extinct notoungulate mammals known from the Late Paleocene to Middle Eocene of Argentina, Bolivia and Brazil. The name honors U.S. paleontologist Henry Fairfield Osborn. Description Henricosborniidae is a grou ...

from the Middle to

Late Paleocene The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...

of South America. Fossils of the genus have been found in the

Mealla Formation The Mealla Formation is a geological formation of the Santa Bárbara Subgroup, part of the Salta Group in the Salta Basin in northwestern Argentina whose strata date back to the Middle to Late Paleocene of the Paleogene. Description The Meal ...

, a

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviog ...

and lacustrine sedimentary unit of the Salta Basin in northwestern

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, th ...

.Sánchez & Marquillas, 2009, p.389Narváez, 2009, p.172 The genus name honors paleontologist George Gaylord Simpson.

Description

''Simpsonotus'' had a skull similar to ''

Notostylops ''Notostylops'' ("south pillar face") is a genus of extinct South American ungulates from Eocene Argentina. Fossils of the genus have been found in the Sarmiento, Casamayor, Andesitas Huancache and Koluel Kaike Formations.

'', but with a shorter and rounder face. The genus contains two species; the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

''S. praecursor'',''S. praecursor''
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.org and the double-sized ''S. major'',''S. major''
at

.org both described by Pascual et al. in 1978.Pascual et al., 1978

Age

The Mealla Formation was initially described as Riochican in the South American land mammal age classification, and later as Itaboraian, but after the redefinition of the

Itaboraí Formation The Itaboraí Formation ( pt, Formação Itaboraí) is a highly list of fossiliferous stratigraphic units in Brazil, fossiliferous geologic Formation (geology), formation and LagerstätteKellner & Campos, 1999, p.399 of the Itaboraí Basin in Rio ...

Early Eocene In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian i ...

, the Mealla Formation is Peligran in age.

References

Bibliography

* * * {{Taxonbar, from=Q96181783 Notoungulates Paleocene mammals of South America Selandian life Thanetian life Peligran Paleogene Argentina Fossils of Argentina Salta Basin Fossil taxa described in 1978 Prehistoric placental genera