''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 nom ...

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 th ...

. It lived during the Late Oligocene, 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 sout ...

. 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. T ...

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 bone ...

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

Adianthus ''Adianthus'' is an extinct genus of litoptern that lived during the Early Miocene to the Middle Miocene in what is now Argentina and Chile. Description This animal is only known from fragmentary remains, mainly from its teeth, and was probabl ...

'' and '' Adiantoides'', 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

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 A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...

; 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 ...

of the second lower molar had a complex structure.

Classification

''Proadiantus'' was one of the

Adianthidae Adianthidae is an extinct family of Litopterna, litopterns that existed from the Middle Eocene (Mustersan) to the Early Miocene (Santacrucian). Description These Arboreal locomotion, scansorial, Viviparity, viviparous animals were actively mobil ...

, 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'' and ''

Tricoelodus ''Tricoelodus'' is an extinct genus of adianthid litopterns that lived during the Late Oligocene in what is now Argentina and Bolivia. Fossils of this genus have been found in the Sarmiento Formation of Argentina and the Salla Formation of Bol ...

''. ''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, especially ...

, based on fossilized remains from the Cabeza Blanca locality of the Sarmiento Formation, 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 rang ...

of Argentine

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 g ...

. 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