''Notoetayoa'' 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 mammal, from the order

Xenungulata Xenungulata ("strange ungulates") is an order of extinct and primitive South American hoofed mammals that lived from the Late Paleocene to Early Eocene (Itaboraian to Casamayoran in the SALMA classification). Fossils of the order are known f ...

. It contains a single species, ''Notoetayoa gargantuai'', which lived during the Middle

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...

. Its fossilized remains were discovered in

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 ...

Description

This animal is only known from a fragment of its jaw, and it is therefore impossible to precisely reconstruct its appearance. From a comparison with a similar but better known animal, ''

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 larg ...

'', it is possible that ''Notoetayoa'' was an animal with heavy shapes and a powerful body. The size of ''Notoetayoa'' was in any cases smaller than that of ''Carodnia'', and it is possible that it was as large as a small

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 ...

. The lower third molar had a higher trigonid than the thalonid, and the paraconid was well defined, and not fused with the metaconid. Compared to its relative ''

Etayoa ''Etayoa'' is an ungulate of the family Carodniidae in the order Xenungulata that lived during the Early Eocene (~ 55 Ma) in northern South America. Etymology The genus of the type species ''Etayoa bacatensis'' was named by palaeontologist C ...

'', its metachristid was short, and the precingulid was more robust than in ''Etayoa'' and ''Carodnia''. The talonid basin wasn't open lingually as in ''Carodnia'', but closed as in ''Etayoa''. The hypoconid and the hypoconulid were distinct and united by a low and rounded postmetacristid. The entoconid was crenulated and mesially projected towards the distal-lingual side of the metoconid. The distal root under the talonid was not vertical as in ''Carodnia'' but oblique to the mesial one.

Classification

''Notoetayoa gargantuai'' was first described in 2008, based on fossilized remains found 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 ...

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

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 ...

, in rocks dated from the Middle Paleocene. ''Notoetayoa'' is considered to be a member of the Xenungulates, an enigmatic group of South American

ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, ...

s of uncertain affinities. In particular, ''Notoetayoa'' is considered very similar to ''Etayoa'', and both genus are sometimes placed within the Etayoidae family. However, compared to its relative, ''Notoetayoa'' was of much larger dimensions. The discovery of ''Notoetayoa'' has expanded the knowledge on Etayoiids both geographically and stratigraphically, as until the description of ''Notoetayoa'' they had only been found further north in Colombia, in more recent soils from the Late Paleocene to the Early Eocene.

References and Bibliography

*J. N. Gelfo, G. M. López, and M. Bond. 2008. A new Xenungulata (Mammalia) from the Paleocene of Patagonia Argentina. Journal of Paleontology 82(2):329-335 *P.-O. Antoine, G. Billet, R. Salas-Gismondi, J. T. Lara, P. Baby, S. Brusset, and N. Espurt. 2015. A New Carodnia Simpson, 1935 (Mammalia, Xenungulata) from the Early Eocene of Northwestern Peru and a Phylogeny of Xenungulates at Species Level. Journal of Mammalian Evolution 22:129-140 {{Taxonbar, from=Q21998094 Meridiungulata Paleocene mammals of South America Paleogene Argentina Fossils of Argentina Fossil taxa described in 2008 Prehistoric placental genera Monotypic mammal genera