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Afrasia djijidae was first described in 2012 on the basis of isolated teeth from the 37-million-year-old
Pondaung Formation, which is close to the village of Nyaungpinle in Myanmar. Prior to the discovery of
A. djijidae, early Asian
simians were typically classified in two
families,
Eosimiidae and
Amphipithecidae. While eosimiids are generally considered the most
basal simian
clade (a
stem group of simians), the
phylogenetic placement of amphipithecids is more disputed. Amphipithecids are usually considered to share affinities with either eosimiids or
crown simians (those simians that are part of the smallest clade that contains the living simians); the latter view is favored. Eosimiids were first described from findings in
China in 1994 and are still best known there (two genera are now known,
Eosimias and
Phenacopithecus), but have also been recorded in
Pakistan (
Phileosimias) and Myanmar (
Bahinia). All species had a small body size and a mix of primitive (ancestral) and
derived traits. The largest eosimiid,
Bahinia, is from the Pondaung Formation, the same
stratum as
Afrasia, and the morphology of its
molars bridges the gap between the more primitive molars of
Eosimias and the more derived molars of the later Eocene African simians.
Afrasia, on the other hand, is more comparable in size to the eosimiids from China. The upper molars of
Afrasia are nearly identical in morphology and size to those of
Afrotarsius, an animal known from 38- to 39-million-year-old deposits in
Libya (species
Afrotarsius libycus) and about 30-million-year-old deposits in
Egypt (
A. chatrathi).
Afrotarsius was originally described as a tarsier, but later suggested to be related to primitive simians. Because of their close similarities,
Afrasia and
Afrotarsius are together placed in the family
Afrotarsiidae. A phylogenetic analysis placed
Afrasia as a
sister group to
Afrotarsius, forming the family Afrotarsiidae. Afrotarsiidae was found to be most closely related to Eosimiidae, and unrelated to tarsiers. The
clade formed by Afrotarsiidae and Eosimiidae was designated as the infraorder
Eosimiiformes by Chaimanee
et al. in 2012. Eosimiiformes are the sister group of crown simians. However, the classification of
Afrotarsius as a stem simian is not accepted by all researchers, and the phylogenetic claims and their implications rest on only the four molars of
Afrasia initially discovered.
Biogeography simians dispersed from Asia to Africa around that time.|alt=Two molars, one of
Afrotarsius (left) and one of
Afrasia (right), are compared, with an Eocene map of the globe showing where each came from. In the lower-left, a life reconstruction of
Afrotarsius is shown. Several hypotheses compete to explain the geographic origins of simians. Of the two most popular views, one hypothesis states that simians originated in Asia, while the other favors Africa as their place of origin. Both their ancient origins and the sparse fossil record in Africa and Asia complicate the debate.
Convergent evolution also makes it difficult for researchers to determine the relationships between fossils. Also, the earliest fossils, which do not match up with
molecular clock estimates for simian origins, have been found in both Afro-Arabia and Asia. At the time, both landmasses would have been separated by the
Tethys Sea. The oldest undisputed simians from Africa also date to the late middle Eocene.
Afrotarsius was found in the
Dur At-Talah escarpment in
Libya, which dates to 38–39 million years ago and also contains the
parapithecid Biretia and the
oligopithecid Talahpithecus. Although diverse, these primates were all very small in size, much like eosimiids. Simian classification for older fossils from Africa are more contested.
Altiatlasius, the oldest suspected fossil primate known from the late
Paleocene of
Morocco, is too fragmentary to ascertain its true affinities.
Algeripithecus was popularly considered an early middle Eocene simian; however, less fragmentary remains uncovered between 2003 and 2009 suggest it was a type of
azibiid, a group of
strepsirrhine primates likely related to
lemuriform primates (
lemurs and
lorisoids). According to the team who discovered
Afrasia, headed by
Jean-Jacques Jaeger, the similarities in tooth morphology, body size, and age suggest a phylogenetic relationship with
Afrotarsius despite the geographic separation. They suggested that afrotarsiid simians from Asia dispersed across the Tethys Sea to Africa around the middle Eocene, giving rise to
Afrotarsius. A reverse migration—as suggested by the hypothesis of the African origin for simians—is not favored due to the close phylogenetic relationship between the older Asian eosimiids and
Afrasia. However, to explain the origins of
Proteopithecidae,
Parapithecidae, and crown simians from the African fossil record, a higher simian clade also needed to disperse from Asia to Africa before the late middle Eocene since neither
Afrasia nor
Afrotarsius could have given rise to this group. Such dispersals from Asia to Africa were not uncommon, since
hystricognathous rodents,
anthracotheres, and possibly other mammalian fauna from Asia arrived around the same time. ==Anatomy==