''Proadiantus'' (Ameghino, 1897) 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 ...

of adianthid

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 ...

. 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 ...

, in what is today

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 souther ...

. It consists of only 1 species, ''Proadiantus excavatus.''

Description

This animal is mainly known from fossil remains of its teeth,

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The ...

and

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bon ...

, and its appearance is therefore difficult to restore. It is assumed, from comparison with its better known relatives '' Adianthus'' and ''

Adiantoides ''Adiantoides'' is an extinct genus of herbivorous mammal, belonging to the order Litopterna. It lived during the Middle to Late Eocene, in South America. Description It was a small-sized animal, only slightly larger than a cat. The skull ...

'', that it was a small and slender litoptern. ''Proadiantus'' differs from ''Adiantoides'' by its significantly larger size, and it may have been as large as a

coyote The coyote (''Canis latrans'') is a species of canine native to North America. It is smaller than its close relative, the wolf, and slightly smaller than the closely related eastern wolf and red wolf. It fills much of the same ecological ni ...

. The

molars The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

had rather low upper crowns ; the upper molars had a mesostyle, but no clearly defined metastyle ; the hypoconus was elongated. The

talonid The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

of the second lower molar had a complex structure.

Classification

''Proadiantus'' was one of the

Adianthidae Adianthidae is an extinct family of litopterns that existed from the Middle Eocene ( Mustersan) to the Early Miocene (Santacrucian). Description These scansorial, viviparous animals were actively mobile and were herbivores. They were small in s ...

, a family of small sized litopterns with a characteristic dentition. ''Proadiantus'' seems to have been one of the most basal members of the group, at the basis of the subfamily Adianthinae. It was closely related to ''

Thadanius ''Thadanius'' is an extinct genus of Litoptern, belonging to the family Adianthidae. It lived during the Late Oligocene, in what is today Bolivia. Description Only known from the fossilized remains of its mandible and teeth, this animal may hav ...

'' and '' Tricoelodus''. ''Proadiantus excavatus'' was first described in 1897 by

Florentino Ameghino Florentino Ameghino (born Giovanni Battista Fiorino Giuseppe Ameghino September 19, 1853 – August 6, 1911) was an Argentine naturalist, paleontologist, anthropologist and zoologist, whose fossil discoveries on the Argentine Pampas, especiall ...

, based on fossilized remains from the Cabeza Blanca locality of the

Sarmiento Formation The Sarmiento Formation (Spanish: ''Formación Sarmiento''), 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- ...

, 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 ...

Argentine Argentines (mistakenly translated Argentineans in the past; in Spanish ( masculine) or ( feminine)) are people identified with the country of Argentina. This connection may be residential, legal, historical or cultural. For most Argentines ...

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and ...

. The species ''Proadiantus pungidens'', described several years later by Ameghino himself based on fossils from the same geological horizon, is now considered identical to the type species.

Bibliography

*F. Ameghino. 1897. Mammiféres crétacés de l’Argentine (Deuxième contribution à la connaissance de la fauna mammalogique de couches à Pyrotherium) retaceous mammals of Argentina (second contribution to the knowledge of the mammalian fauna of the Pyrotherium Beds) Boletin Instituto Geografico Argentino 18(4–9):406-521 *F. Ameghino. 1901. Notices préliminaires sur des ongulés nouveaux des terrains crétacés de Patagonie reliminary notes on new ungulates from the Cretaceous terrains of Patagonia Boletin de la Academia Nacional de Ciencias de Córdoba 16:349-429 *G. G. Simpson and J. L. Minoprio. 1949. A new adianthine litoptern and associated mammals from a Deseadan faunule in Mendoza, Argentina. American Museum Novitates 1434:1-27 *R. L. Cifelli and M. F. Soria. 1983
Systematics of the Adianthidae (Litopterna, Mammalia)
American Museum Novitates 2771:1-25

References

{{Taxonbar, from=Q110464870 Litopterns Oligocene mammals of South America Paleogene Argentina Fossils of Argentina Fossil taxa described in 1897 Taxa named by Florentino Ameghino Prehistoric placental genera Golfo San Jorge Basin Sarmiento Formation