Convergent evolution of anthropoid-like adaptations in Eocene adapiform primates

Adapiform or 'adapoid' primates first appear in the fossil record in the earliest Eocene epoch (∼55 million years (Myr) ago), and were common components of Palaeogene primate communities in Europe, Asia and North America¹. Adapiforms are commonly referred to as the 'lemur-like' primates of the Eocene epoch, and recent phylogenetic analyses have placed adapiforms as stem members of Strepsirrhini^2-4, a primate suborder whose crown clade includes lemurs, lorises and galagos. An alternative view is that adapiforms are stem anthropoids⁵. This debate has recently been rekindled by the description of a largely complete skeleton of the adapiform Darwinius⁶, from the middle Eocene of Europe, which has been widely publicised as an important 'link' in the early evolution of Anthropoidea ⁷. Here we describe the complete dentition and jaw of a large-bodied adapiform (Afradapis gen. nov.) from the earliest late Eocene of Egypt (∼37 Myr ago) that exhibits a striking series of derived dental and gnathic features that also occur in younger anthropoid primates-notably the earliest catarrhine ancestors of Old World monkeys and apes. Phylogenetic analysis of 360 morphological features scored across 117 living and extinct primates (including all candidate stem anthropoids) does not place adapiforms as haplorhines (that is, members of a TarsiusAnthropoidea clade) or as stem anthropoids, but rather as sister taxa of crown Strepsirrhini; Afradapis and Darwinius are placed in a geographically widespread clade of caenopithecine adapiforms that left no known descendants. The specialized morphological features that these adapiforms share with anthropoids are therefore most parsimoniously interpreted as evolutionary convergences. As the largest non-anthropoid primate ever documented in AfroArabia, Afradapis nevertheless provides surprising new evidence for prosimian diversity in the Eocene of Africa, and raises the possibility that ecological competition between adapiforms and higher primates might have played an important role during the early evolution of stem and crown Anthropoidea in Afro-Arabia.