''Colbertia'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

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 oldfieldthomasiid notoungulate. It lived from the Early to the Middle

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

, and its fossilized remains were discovered in

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 ...

and

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

Description

This animal was roughly the size of a

Virginia opossum The Virginia opossum (''Didelphis virginiana''), also known as the North American opossum, is the only opossum living north of Mexico, its range extending south into Central America. It is the northernmost marsupial in the world. In the United S ...

, reaching approximately 50 centimeters in length excluding its tail. Its weight has been estimated to have been around 2 to 3 kilograms. ''Colbertia'' had a relatively elongated skull, with low-crowned (brachydont) molars ; the cusps of the molars were joined to form ridge-like structures called lophs, and are therefore considered lophodont. The paracone and the metacone had notable folds. The ankle bones of ''Colbertia'' indicates that it was a plantigrade, an ancestral condition within Notoungulata. The bone morphology at the base of the skull was very similar to other basal Notoungulates, although the petrous bone had distinct characteristics also found in similar but slightly more recent notoungulates, such as '' Dolichostylodon''.

Classification

The genus ''Colbertia'' was first described in 1952 by

Carlos de Paula Couto Carlos de Paula Couto, (Porto Alegre, August 30, 1910 – November 15, 1982) was a Brazilian paleontologist. Biography Paula Couto was a researcher at the National Museum of Brazil in Rio de Janeiro, specialized in paleontology of mammals. ...

, as a new genus for a species of notoungulate described two years earlier and attributed to the genus ''Oldfieldthomasia'' as ''O. magellanica''. The type species of the genus is ''Colbertia magellanica'', from the Early Eocene

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 ...

. Fossils attributed to other species, ''C. lumbrerense'' and ''C. falui'', have been discovered in

in slightly younger deposits, from the Middle Eocene. ''Colbertia'' is a basal member of the suborder

Typotheria Typotheria is a suborder of the extinct mammalian order Notoungulata Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,0 ...

, a group of notoungulates sharing similarities with

hyrax Hyraxes (), also called dassies, are small, thickset, herbivorous mammals in the order Hyracoidea. Hyraxes are well-furred, rotund animals with short tails. Typically, they measure between long and weigh between . They are superficially simil ...

es and

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

s. ''Colbertia'' was a basal member of this clade, within the family

Oldfieldthomasiidae Oldfieldthomasiidae is an extinct family of notoungulate mammals known from the Late Paleocene to Late Eocene of South America. The family was classified by George Gaylord Simpson in 1945 and a synonym is Acoelodidae, defined by Florentino Ameghi ...

, which may be paraphyletic. ''Colbertia'' may have been close to the most basal typothere, who subsequently derived and diversified considerably to occupy a variety of ecological niches.

Paleoecology

''Colbertia'' was a terrestrial, herbivorous mammal, with a diet composed of tender leaves, buds and flowers.

Bibliography

*C. d. Paula Couto. 1952. Fossil mammals from the beginning of the Cenozoic in Brazil. Notoungulata. American Museum Novitates 1568:1-16 *M. Bond. 1981. Un nuevo Oldfieldthomasiidae (Mammalia, Notoungulata) del Eoceno inferior (Fm. Lumbrera, Grupo Salta) del NW Argentino. II Congresso Latino-Americano de Paleontología 2:521-536 *D. A. García López. 2011. Basicranial Osteology of Colbertia lumbrerense Bond, 1981 (Mammalia: Notoungulata). Ameghiniana 48(1):3-12 *Fernández, M.; Zimicz, A. N.; Bond, M.; Chornogubsky, L.; Arnal, M.; Cárdenas, M.; Fernicola, J. C. (2021). "New Eocene South American native ungulates from the Quebrada de los Colorados Formation at Los Cardones National Park, Argentina". Acta Palaeontologica Polonica. 66 (1): 85–97. doi:10.4202/app.00784.2020. {{Taxonbar, from=Q16550186 Typotheres Eocene mammals of South America Paleogene Argentina Fossils of Argentina Fossils of Brazil Paleogene Brazil Mustersan Casamayoran Itaboraian Fossil taxa described in 1952 Prehistoric placental genera Itaboraí Formation