''Altanius'' is a genus of extinct primates found in the early

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'', " ...

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

. Though its phylogenetic relationship is questionable, many have placed it as either a primitive omomyid or as a member of the sister group to both adapoids and omomyids.Mikko's Phylogeny Archive
/ref> The genus is represented by one species, ''Altanius orlovi'', estimated to weigh about 10–30g from relatively well-known and complete dental and facial characteristics.

Morphology

Much of the fossilized remains of ''Altanius'', as with any extinct vertebrate, are isolated teeth fragments. However, an abundance of specimens, collected between Dashzeveg and McKenna's initial discovery of the species in 1977 and the present, have yielded an almost complete dentition. Identifying dental characteristics of the genus include small, high,

trigonid 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 ...

s, the anterior basin on lower molars, and high premolars. It is linked with the omomyoid group in its unfused

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

, reduced paraconids on the lower molars, and overall shorter molars. These traits are too numerous to have been easily developed by

parallel evolution Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and paral ...

. In the taxa's four premolars, double rooted second premolar and unreduced canine and last molar, the teeth of ''Altanius'' are too primitive to be omomyoids, best resembling the

Carpolestidae Carpolestidae is a family of primate-like Plesiadapiformes that were prevalent in North America and Asia from the mid Paleocene through the early Eocene. Typically, they are characterized by two large upper posterior premolars and one large lo ...

, a group of Plesiadapiformes. The dentition is also not dissimilar from primitive adapoids '' Donrusselia'' and ''

Cantius ''Cantius'' is a genus of adapiform primates from the early Eocene of North America and Europe. It is extremely well represented in the fossil record in North America and has been hypothesized to be the direct ancestor of Notharctus in North Amer ...

''. However, its high lingual cusps and short

talonid 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 ...

s, the basin at the distal end of the lower molars, are traits too derived for this specimen to be a primitive omomyoid ancestor.

Phylogeny

Found in 1977, this genus was one of the first Eocene fossil primates to be found in Asia and indicates that early primate radiations were not restricted to North America and Europe. ''Altanius'', with a mixture of dental traits, some incredibly primitive, some very similar to other omomyoids, and some highly specialized, has not been satisfactorily placed in any taxonomic group. Most likely, it is a member sister group that branched off either right before or right after the omomyoid/adapoid split, although there are many other interpretations.

Morphology

Phylogeny

References

Further reading