''Surameryx'' 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 herbivorous

even-toed ungulate The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...

s originally described as belonging to the extinct

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Palaeomerycidae. A single species, ''S. acrensis,'' was described from the Late Miocene (between the

Mayoan The Mayoan ( es, Mayoense) age is a period of geologic time from 11.8 to 10 Ma, within the Middle to Late Miocene epoch of the Neogene, used more specifically within the SALMA classification in South America. It follows the Laventan and precedes ...

and

Huayquerian The Huayquerian ( es, Huayqueriense) age is a period of geologic time (9.0–6.8 Ma) within the Late Miocene epoch of the Neogene, used more specifically within the SALMA classification. It follows the Mayoan The Mayoan ( es, Mayoense) age is ...

SALMA, between 11.6 to 5.3 million years ago) of the Madre de Dios Formation,

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 was originally interpreted as one of the few northern mammals that entered South America before the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Donald R. Prothero , Kenneth E. Campbell, Jr. , Brian L. Beatty , and Carl D. Frailey. 2014
New late Miocene dromomerycine artiodactyl from the Amazon Basin: implications for interchange dynamics
''Journal of Paleontology'', 88(3):434–443. However, both its identification as a member of the family Palaeomerycidae and claims about its Miocene age were subsequently challenged.

Description

''Surameryx'' is known from the left half of the nearly complete lower jaw, reminiscent of the North American palaeomerycids, which are known from numerous fossils. The jaw of ''Surameryx'' is similar to that of '' Barbouromeryx'' in having a premolar row without reduction compared to the molar row; additionally it showed the characteristic "'' Palaeomeryx'' fold", a typical molar crest present in various types of primitive

ruminant Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The ...

s, and a vertical groove on the back or inner surface of the fourth premolar. ''Surameryx'' still differs from its relatives in the much wider shape of the molars and premolars, and in its shorter, upward recurved coronoid process; the stylids were also higher than in other related genera.

Taxonomy

''Surameryx acrensis'' was first named and described in 2014, based on the fossil jaw discovered in the Madre de Dios Formation extending along the

Acre River The Acre River (called Aquiry in the local Iñapari language; locally, ''Rio Acre'') is a long river in central South America. Course The river is born in Peru, and runs North-Eastwards, forming part of the border between Peru and Brazil and the ...

in the area between

Cobija Cobija is a city in Bolivia, capital of the department of Pando, is located about 600 km (373 mi.) north of La Paz in the Amazon Basin on the border with Brazil. Cobija lies on the banks of the Rio Acre across from the Brazilian ci ...

, Bolivia and

Assis Brasil Assis Brasil () is a Municipalities of Brazil, municipality located in the south of the States of Brazil, Brazilian state of Acre (state), Acre. Its population is 7,534 (2020 est) and its area is . The municipality contains part of the Rio Ac ...

. ''Surameryx'' is a representative of the palaeomerycids, an extinct family of Miocene

artiodactyl The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...

s related to cervids and giraffids. More specifically, ''Surameryx'' was a member of the dromomerycines, a group of palaeomerycids endemic to North America; within these, it seems to have a close relationship with ''Barbouromeryx trigonocorneus'', a primitive dromomerycine of the middle Miocene (20–16 million years ago). The name ''Surameryx'' is derived from the

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...

word ''sur'' ("south") and the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''meryx'' ("ruminant"); the species name ''acrensis'' refers to the Acre River.

Relevance

If confirmed, the discovery of a dromomerycine in South America would be exceptional; until 2014 there were only sporadic findings of placental mammals other than xenarthrans or

meridiungulates South American native ungulates, commonly abbreviated as SANUs, are extinct ungulate-like mammals of controversial affinities that were indigenous to South America prior to the Great American Biotic Interchange. They comprise five major groups c ...

in South America in layers earlier than the Pliocene epoch. While the

Great American Biotic Interchange The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which lan ...

is traditionally regarded as an event of the late Pliocene (about 3 million years ago), it actually started much earlier, going back at least to the late Miocene, about 10 million years ago. The presence of ''Surameryx'' in the Amazon basin is evidence of this exchange in the Miocene, which had already been suggested by the presence of contemporary specimens of gomphotheriids ('' Amahuacatherium''),

peccaries A peccary (also javelina or skunk pig) is a medium-sized, pig-like hoofed mammal of the family Tayassuidae (New World pigs). They are found throughout Central and South America, Trinidad in the Caribbean, and in the southwestern area of North ...

('' Sylvochoerus'' and '' Waldochoerus'') and

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 ...

s and presence around the same time of ground sloths in North America ('' Thinobadistes'' and ''

Pliometanastes ''Pliometanastes'' is an extinct genus of ground sloths of the family Megalonychidae endemic to North America during the Late Miocene epoch through very early Pliocene epoch ( Hemphillian in the NALMA classification). Its fossils have been foun ...

'').McDonald, H. G. 2005. Paleoecology of extinct xenarthrans and the Great American Biotic Interchange. ''Bulletin of the Florida Museum of Natural History'' 45, 313–333. It seems that the paleomerycids were unable to successfully colonize South America, while other groups fared better there. Proboscideans survived until the arrival of humans) and peccaries and tapirs currently live in South America. However, the dating of the putative Miocene fossil beds in western Amazonia and the identification of the gomphothere remains as ''Amahuacatherium'' have been challenged. Gasparini ''et al.'' (2021) reevaluated the fossil material of ''S. acrensis'', and argued that dental characters used to assign this species to Dromomerycinae by Prothero ''et al.'' (2014) are not diagnostic, and can be also found in other groups of even-toed ungulates, including South American deers. The authors also noted that the teeth of the holotype specimen of ''S. acrensis'' are very worn and the heavy wear has played a part in confounding and obscuring some of the dental features. In addition, Gasparini ''et al.'' considered the provenance and age of known fossil material of ''S. acrensis'' to be dubious. The authors believed that the original interpretation of the holotype specimen of ''S. acrensis'' as a dromomerycine was heavily influenced by its supposed Miocene age. According to Gasparini ''et al.'', if the preserved morphology of the holotype specimen of ''S. acrensis'' is the only information considered, it is best interpreted as fossil material of a deer of uncertain specific identity, likely an old individual with a dental age greater than seven years. The authors considered it more likely that this specimen was of Quaternary rather than Miocene age.

References

{{Taxonbar, from=Q18420540 Palaeomerycidae Prehistoric even-toed ungulate genera Miocene mammals of South America Huayquerian Chasicoan Mayoan Neogene Brazil Fossils of Brazil Fossil taxa described in 2014