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 n ...
of
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 resem ...
, belonging to the suborder Typotheria. It lived during the Middle
Eocene
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...
, 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, t ...
.
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 (biology), 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 roden ...
s, and weighing less than two kilograms. The snout was higher than in '' Notopithecus'', 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 skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more p ...
. 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
''Oldfieldthomasia'' is an extinct genus of Notoungulate, probably related to the suborder Typotheria. It lived during the Middle Eocene, in what is today South America.
Description
This animal was approximately the size of a marmot, and probab ...
'', 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, especiall ...
. It is known from various fossils discovered in Middle Eocene terrains of
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 ...
. 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 incom ...
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 resem ...
. 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 si ...
'', 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, a group of rodent-like notoungulates.