''Archaeopithecus'' 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 ...

Notoungulate Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resemb ...

, belonging to the suborder

Typotheria Typotheria is a suborder of the extinct mammalian order Notoungulata Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,0 ...

. It lived during the Middle

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

, in what is today

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 ...

Description

This animal is mostly known from several cranial remains, including an almost complete skull, teeth and mandibles. Comparison with some of its better known relatives allows to portray a small animal, somewhat similar with

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

s, and weighing less than two kilograms. The snout was higher than in ''

Notopithecus ''Notopithecus'' is an extinct genus of Notoungulate, belonging to the suborder Typotheria. It lived from the Middle to the Late Eocene and its fossilized remains were discovered in South America. Description This animal is known from numerous ...

'', with a longer rostrum ; the mandible was short and thick, with a particularly massive, short and broad

mandibular symphysis In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral halves ...

. The tympanic bullae were modestly sized. ''Archaeopithecus'' had conical incisors, similar to its canines, and triangular-shaped upper premolars, devoid of hypocone. The premolars and molars had a strong parastyle and a paracone fold. Unlike other Eocene notoungulates such as ''Notopithecus'' and '' Oldfieldthomasia'', which had low-crowned teeth, ''Archaeopithecus'' had a near-hypsodont (high-crowned) dentition, with short diastemas between the anterior teeth. The teeth of ''Archaeopithecus'' show an important occlusal variability during growth, associated with a variations caused by wear in the size of the teeth : with the progress of dental wear, the upper molars became wider, while the lower molars became broad and short.

Classification

The type species, ''Archaeopithecus rongeri'', 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 ...

. It is known from various fossils discovered in Middle Eocene terrains of

. More recently, other species of small notoungulates from the same terrains were described, including ''Acropithecus tersus'' and ''Archaeopithecus rigidus''. Several studies tried subsequently to shed light on their taxonomic confusion ; a recent review of their fossil materials indicates that all those species are most probably synonymous with the type species.B. Vera. 2017. Patagonian Eocene Archaeopithecidae Ameghino, 1897 (Notoungulata): systematic revision, phylogeny and biostratigraphy. Journal of Paleontology ''Archaeopithecus'' and ''Acropithecus'' were initially described by Ameghino as primitive

monkey Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incomple ...

s, hence their name, ''Archaeopithecus'' ("archaic monkey") and ''Acropithecus'' ("highest monkey"), but were later correctly attributed to the order

Notoungulata Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resemb ...

. There is still doubts over the real relationships of this genus within Notoungulata ; it is often placed, with its relative ''

Teratopithecus ''Teratopithecus'' is an extinct genus of archaeopithecid notoungulate that lived during the Middle Eocene of what is now Argentina. Fossils of this genus have been found in the Sarmiento Formation of Argentina. Description This animal was sim ...

'', within the family

Archaeopithecidae Archaeopithecidae is an extinct family comprising two genera of notoungulate mammals, '' Teratopithecus'' and '' Archaeopithecus'', both known from the Eocene of Argentina.Typotheria Typotheria is a suborder of the extinct mammalian order Notoungulata Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,0 ...

, a group of rodent-like notoungulates.

References

*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. 1904. Nuevas especies de mamíferos, cretáceos y terciarios de la República Argentina ew species of mammals, Cretaceous and Tertiarty, from the Argentine Republic Anales de la Sociedad Cientifica Argentina 56–58:1-142 *G. G. Simpson. 1967. The beginning of the age of mammals in South America. Part II. Bulletin of the American Museum of Natural History 137:1-260 *B. Vera. 2016. Phylogenetic revision of the South American notopithecines (Mammalia: Notoungulata). Journal of Systematic Palaeontology 14:461-480. {{Taxonbar, from=Q60977826 Typotheres Eocene mammals of South America Paleogene Argentina Fossils of Argentina Taxa named by Florentino Ameghino Fossil taxa described in 1897 Prehistoric placental genera Golfo San Jorge Basin Sarmiento Formation