Xenungulata ("strange ungulates") is an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

of extinct and

primitive Primitive may refer to: Mathematics * Primitive element (field theory) * Primitive element (finite field) * Primitive cell (crystallography) * Primitive notion, axiomatic systems * Primitive polynomial (disambiguation), one of two concepts * Pr ...

South American hoofed mammals that lived from the

Late Paleocene The Thanetian is, in the ICS Geologic timescale, the latest age or uppermost stratigraphic stage of the Paleocene Epoch or Series. It spans the time between . The Thanetian is preceded by the Selandian Age and followed by the Ypresian Age (part ...

Early Eocene In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

( Itaboraian to Casamayoran in the SALMA classification). Fossils of the order are known from deposits in

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 ...

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, t ...

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

, and Colombia. The best known member of this enigmatic order is the genus ''

Carodnia ''Carodnia'' is an extinct genus of South American ungulate known from the Early Eocene of Brazil, Argentina, and Peru. ''Carodnia'' is placed in the order '' Xenungulata'' together with '' Etayoa'' and '' Notoetayoa''. ''Carodnia'' is the lar ...

'', a

tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a pig, with a short, prehensile nose trunk. Tapirs inhabit jungle and forest regions of South and Central America, with one species inh ...

-like and -sized animal with a gait similar to living African elephants.

Description

Xenungulates are characterized by

bilophodont 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 ...

M^1–2 and M_1–2, similar to

pyrotheres Pyrotheria is an order of extinct meridiungulate mammals. These mastodon-like ungulates include the genera ''Baguatherium'', ''Carolozittelia'', ''Colombitherium'', ''Griphodon'', ''Propyrotherium'', ''Proticia'', and ''Pyrotherium''. They had ...

, and complex lophate third molars, similar to

uintatheres Uintatheriidae is a family of extinct ungulate mammals that includes ''Uintatherium''. Uintatheres belong to the order Dinocerata, one of several extinct orders of primitive hoofed mammals that are sometimes united in the Condylarthra. Uintathe ...

. Though other relationships, to arctocyonids for example, have been suggested, no proofs thereof have been found. The foot bones of xenungulates were short and robust and their digits terminated in broad, flat, and unfissured hoof-like unguals, quite unlike any other meridiungulates. The discovery of '' Etayoa'' in Colombia made it clear that xenungulates are distinct from other groups: ''Etayoa'' lacks lophate molar talonid (in contrast to ''Carodnia'') and, since no distinct lophodonty is present in basal pyrotheres, there is reason to assume that bilophodonty evolved separately in xenungulates and pyrotheres. Xenungulates also show some dental similarity to primitive

astrapotheres Astrapotheria is an extinct order of South American and Antarctic hoofed mammals that existed from the late Paleocene to the Middle Miocene, ."The uruguaytheriine Astrapotheriidae from the rich middle Miocene Honda Group of the upper Magdalena R ...

Taxonomy

grouped ''Carodnia'' with

based on a similarity in

astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to te ...

morphology, but later concluded that this observation was incorrect. '' Notoetayoa'' is most closely related to ''Etayoa''.

Distribution

Xenungulata fossils have been found in:Xenungulata
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cre ...

.org * Bogotá Formation, Casamayoran, Colombia *

Peñas Coloradas Formation Peñas is a location in the La Paz Department in 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 Boliv ...

, Riochican, Argentina *

Mogollón Formation Mogollon may refer to: Anthropology * Mogollon culture (c. 200–1500 CE), a culture in what is now Northern Mexico and the Southwestern United States Cryptozoology * Mogollon Monster, a legendary creature that has been discussed in accoun ...

, Itaboraian- Riochican, Peru * Itaboraí Formation, Itaboraian, Brazil

References

Bibliography

* * * * * * * * * {{Taxonbar, from=Q142395 Meridiungulata Paleocene mammals of South America Eocene mammals of South America Paleocene first appearances Eocene extinctions Casamayoran Itaboraian Riochican Fossil taxa described in 1952