Anthropoid versus strepsirhine status of the African Eocene primates Algeripithecus and Azibius : craniodental evidence

Abstract

Recent fossil discoveries have demonstrated that Africa and Asia were epicentres for the origin and/or early diversification of the major living primate lineages, including both anthropoids (monkeys, apes and humans) and crown strepsirhine primates (lemurs, lorises and galagos). Competing hypotheses favouring either an African or Asian origin for anthropoids rank among the most hotly contested issues in paleoprimatology. The Afrocentric model for anthropoid origins rests heavily on the .45 Myr old fossil Algeripithecus minutus from Algeria, which is widely acknowledged to be one of the oldest known anthropoids. However, the phylogenetic position of Algeripithecus with respect to other primates has been tenuous because of the highly fragmentary fossils that have documented this primate until now. Recently recovered and more nearly complete fossils of Algeripithecus and contemporaneous relatives reveal that they are not anthropoids. New data support the idea that Algeripithecus and its sister genus Azibius are the earliest offshoots of an AfroArabian strepsirhine clade that embraces extant toothcombed primates and their fossil relatives. Azibius exhibits anatomical evidence for nocturnality. Algeripithecus has a long, thin and forwardly inclined lower canine alveolus, a feature that is entirely compatible with the long and procumbent lower canine included in the toothcomb of crown strepsirhines. These results strengthen an ancient African origin for crown strepsirhines and, in turn, strongly challenge the role of Africa as the ancestral homeland for anthropoids.

Primate origins, human origins, and the end of higher taxa

“…Although their affinities are widely debated, most of the fragmentary early (Paleocene to mid-Eocene) fossils that have been proposed recently as candidate basal anthropoids (Eosimias, Algeripithecus, Biretia, Altiatlasius, Anthrasimias) exhibit some combination of diminutive size, moderately trenchant cheek teeth, and enlarged orbits, suggesting derivation from a small, visually predatory ancestor. 101,[108][109][110][111][112][113] Can we then still attribute the origin of the distinctive euprimate traits to a basal adaptive shift involving visually directed predation? I am now inclined to think that the whole notion of a defining adaptive shift that accounts for ''primate origins'' is another hallucination born of ignorance.…”

New perspectives on anthropoid origins

“…Afrotarsius, from the Egyptian Oligocene, resembles stem anthropoids (41), but also tarsiids (13,42). Algeripithecus (early to middle Eocene, Algeria) was commonly recognized as an anthropoid (39), but recent discoveries of more complete specimens suggest that it is not anthropoid but instead may belong to the Azibiidae (43). Azibiids are argued to be adapiforms, early euprimates, plesiadapiforms (possible stem primates), or even nonprimates (14,44,45), and there is no consensus on their phylogenetic position.…”

“…Azibiids are argued to be adapiforms, early euprimates, plesiadapiforms (possible stem primates), or even nonprimates (14,44,45), and there is no consensus on their phylogenetic position. However, the oblique orientation of the lacrimal canal relative to the infraorbital canal indicates that they are not crown haplorhines (Tarsius and anthropoids have more vertically oriented lacrimal canals) (43). Specimens attributed to another supposed anthropoid from Algeria, Tabelia, are probably specimens of Algeripithecus or Azibius (43).…”

Late Middle Eocene primate from Myanmar and the initial anthropoid colonization of Africa

“…However, decisive progress has recently been achieved in understanding some of the earliest purported African anthropoids. Algeripithecus, which was originally described on the basis of two isolated molars as an early middle Eocene African anthropoid (13), is now recognized as a strepsirrhine, following the discovery of more nearly complete material (14). Other African fossil sites that are older than late middle Eocene, such as the Chambi locality in Tunisia, have so far yielded only strepsirrhine primates (15).…”