Altiatlasius is an extinct genus of mammal, which may have been the oldest known primate, dating to the Late Paleocene from Morocco. The only species, Altiatlasius koulchii, was described in 1990. Its true taxonomic position remains controversial. It has also been suggested that it should be classified as a plesiadapiform or that it should be recognized as a euprimate, either as an omomyid, an early tarsiiform, or the oldest stemsimian.
Altiatlasius koulchii, potentially the oldest known euprimate, is known only from ten isolated upper and lower molars and a fragment of a mandible. These fossils date to the Late Paleocene, approximately 57million years ago, and come from the Jbel Guersif Formation in the Ouarzazate Basin of Morocco. First described in 1990 by Sigé et al., Altiatlasius was originally proposed to be an omomyid, possibly close to the split with simians. It has also been classified in the familyToliapinidae, a type of plesiadapiform found in Europe. Other classifications assume they are stem euprimates, eosimiid-like simians, or an early tarsiiform. Many authorities consider Altiatlasius to be the oldest stem simian. Godinot and Bajpai et al. both support the view that it is an early anthropoid. Together with the Early to Middle Eocenefossil primate Algeripithecus from Algeria, Altiatlasius helped strengthen the argument for an African origin of simian primates. However, when additional fossil remains of Algeripithecus were found, it was shown to be a strepsirrhine primate instead of a haplorhine, placing it with the azibiids, a group thought to be most closely related to lemuriforms. Because Algeripithecus was radically reclassified with the discovery of more fossils, equally fragmentary remains of Altiatlasius leave its phylogenetic affinities questionable. Also, the 20 million year gap in the fossil record between Altiatlasius and the first parapithecoids raises questions about the validity of the African origins hypothesis for simians.
