''Thadanius'' 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 ...

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 ...

, belonging to the family

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 ...

. 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 ...

, in what is today

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

Description

Only known from the fossilized remains of its mandible and teeth, this animal may have been similar to its 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 ''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 wa ...

'', and probably was a small animal, the size of a small dog and slender in build. ''Thadanius'' was characterized by moderately high crowned teeth ; the lower molars were devoid of anterior cingulum, while the hypoconulid was not expanded as in other contemporary

, such as ''

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 ...

'' and ''

Proadiantus ''Proadiantus'' (Ameghino, 1897) is an extinct genus of adianthid litoptern. It lived during the Late Oligocene, in what is today South America. It consists of only 1 species, ''Proadiantus excavatus.'' Description This animal is mainly kno ...

'' to form a third lobe on the third molar. The entoconid did not reach the apex of the hypoconulid, but was connected to an hypoconulid-entoconid crest, and a rudimentary entolophid was present, especially on the third lower molar. There was no basin on the lower third molar.

Classification

''Thadanius'' was a member of the

, a clade of small-sized litopterns that went extinct during the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

period. ''Thadanius'' shares similarities with ''Proadiantus'', and they may have been related, as ''Tricoelodus''. ''Thadanius'' was first described in 1983, based on fragmentary remains from the

Salla Formation Salla (''Kuolajärvi'' until 1936) ( smn, Kyelijävri) is a municipality of Finland, located in Lapland. The municipality has a population of () and covers an area of of which is water. The population density is . The nearby settlement of Sa ...

, in the

Loayza Province Loayza or José Ramón Loayza is a province in the La Paz Department, Bolivia. Its seat is Luribay. Geography The Kimsa Cruz mountain range traverses the province. Some of the highest mountains of the province are listed below: Subdivisio ...

, in terrains dated from the Late Oligocene. Its name is an

anagram An anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once. For example, the word ''anagram'' itself can be rearranged into ''nag a ram'', also the word ...

of ''Adianthus'', the eponymous genus of Adianthidae.R. L. Cifelli and M. F. Soria. 1983. Systematics of the Adianthidae (Litopterna, Mammalia). American Museum Novitates 2771:1-25

References

{{Taxonbar, from=Q110465319 Litopterns Oligocene mammals of South America Paleogene Bolivia Fossils of Bolivia Fossil taxa described in 1983 Prehistoric placental genera