Altanius is a genus of extinct primates found in the early Eocene of Mongolia. Though its phylogenetic relationship is questionable, many have placed it as either a primitive omomyid

Omomyid

Omomyids are a diverse group of early primates that radiated during the Eocene epoch between about 55 and 34 million years ago . Fossils of omomyids are found in North America, Europe, Asia, and possibly Africa...

 or as a member of the sister group to both adapoids and omomyids. The genus is represented by one species, Altanius orlovi, estimated to weigh about 10g 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, trigonids, the anterior basin on lower molars, and high premolars. It is linked with the omomyoid group in its unfused mandible

Mandible

The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

, 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

Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...

. In the taxa's 4 premolars, double rooted 2nd premolar and unreduced canine and last molar, the teeth of Altanius are too primitive to be omomyoids, best resembling the Carpolestidae

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 lower posterior premolar. They weighed about 20-150g, and...

, a group of Plesiadapiformes

Plesiadapiformes

Plesiadapiformes is an extinct order of mammals. It is either closely related to the primates or a precursor to them. Many are too derived to be ancestral to primates, but the earliest Plesiadapiformes have teeth that are strongly indicative of a common ancestor...

. The dentition is also not dissimilar from primitive adapoids Donrusselia and Cantius

Cantius

Cantius was a genus of adapiformes primate that lived in the Eocene....

. However, its high lingual cusps and short talonids, 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.