''Elmerriggsia'' 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 ...

Notoungulate 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 11,000 years ago. Notoungulates were morphologically diverse, with forms resemb ...

, belonging to the family

Leontiniidae Leontiniidae is an extinct family comprising eighteen genera of notoungulate mammals known from the Middle Eocene (Mustersan) to Late Miocene (Huayquerian) of South America South America is a continent entirely in the Western Hemisphe ...

. It lived during the Late

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

Description

This animal, like all leontiniids, had a fairly robust body and strong legs. Unlike most of its relatives, however, ''Elmerriggsia'' was less than 1,5 meters long. ''Elmerriggsia'' had the V-shaped skull when viewed from above, the canine-shaped upper incisors (as well as the third lower incisor), and the mesodont typed dentition characteristic of all leontiniids. The skull of ''Elmerriggsia'' was characterized by the presence of premolars with a grooved protocone, without an intermediate lingual cingulum, and by a well developed labial cingulum on the lower molars. These dental features distinguished ''Elmerriggsia'' from any other leontiniids.

Classification

''Elmerriggsia fieldia'' was first described in 2012, based on fossil remains found near

Pico Truncado Pico Truncado is a town and municipality in Santa Cruz Province in southern Argentina. In 1921, the village's railway station was the site of one of the few open engagements between the Argentine Army and anarchist strikers at the time of the e ...

in the Santa Cruz Province of

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 ...

, in terrains dated from the

Deseadan The Deseadan ( es, Deseadense) age is a period of geologic time (29.0–21.0 Ma) 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 fo ...

(Late

). The fossils had been discovered over 75 years earlier, during an expedition to Argentina organized in 1924 by the

Field Museum The Field Museum of Natural History (FMNH), also known as The Field Museum, is a natural history museum in Chicago, Illinois, and is one of the largest such museums in the world. The museum is popular for the size and quality of its educational ...

and led by

Elmer S. Riggs Elmer Samuel Riggs (January 23, 1869 – March 25, 1963) was an American paleontologist known for his work with the Field Museum of Natural History in Chicago, Illinois. Biography He was born in Trafalgar, Indiana, and moved with his family ...

, and were informally known as ''Leontinia'' sp.. Various fossils attributed to this animal were not only discovered near Pico Truncado, but also in various other areas of Argentina. ''Elmerriggsia'' was a rather basal leontiniid, despite its Late Oligocene age ; according to a cladistic analysis carried out in 2012, ''Elmerriggsia'' was part of a basal clade of leontiniids, shared with the

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' ...

genera ''

Martinmiguelia ''Martinmiguelia'' is an extinct genus of Notoungulate, belonging to the family Leontiniidae. It lived during the Middle Eocene, and its fossil remains were found in South America. Description This animal is only known from skull and mandible r ...

'' and ''

Coquenia ''Coquenia'' is an extinct genus of Notoungulate, belonging to the family Leontiniidae. It lived during the Middle Eocene, in what is today Argentina. Description Known only from skull and mandible remains, ''Coquenia'' may have been a heavily ...

''.

Bibliography

*B. J. Shockey, J. J. Flynn, D. A. Croft, P. Gans, and A. R. Wyss. 2012. New leontiniid Notoungulata (Mammalia) from Chile and Argentina: comparative anatomy, character analysis, and phylogenetic hypotheses. American Museum Novitates 3737:1-64 {{Taxonbar, from=Q97371617 Toxodonts Oligocene mammals of South America Paleogene Argentina Fossils of Argentina Fossil taxa described in 2012 Prehistoric placental genera