Anatomy, Systematics, and Evolution of Catarrhines from the Late Oligocene and Early Miocene of Eastern Africa

Abstract

The early Miocene catarrhines are key taxa for elucidating the evolutionary history of the Hominoidea and Cercopithecoidea because they are temporally and morphologically intermediate between more primitive Oligocene faunas and modern primate communities. However, insight into the adaptive processes that led to the living catarrhine clades is obscured because of confusion over both taxonomic diversity and systematic affinities within key early Miocene groups. The research presented in this dissertation takes advantage of the increase in new, more complete fossils and taxa to overcome these limitations. The small catarrhines and nyanzapithecines are revised following a comprehensive review, resulting in the description of two new genera (Gen. nov. A and Gen. nov. B), a new species of Dendropithecus, and transfer of Nyanzapithecus harrisoni to Turkanapithecus. This revision provides evidence for increased geographic and ecological differentiation among sympatric small catarrhines, nyanzapithecines, and large-bodied hominoids during the early Miocene. A new phylogenetic analysis using maximum parsimony includes 64 taxa and 243 characters, and recovered a well-resolved consensus tree (MPTs = 18, 901 steps long) that supports monophyly of Cercopithecoidea and Hominoidea. Within Hominoidea, the Pliopithecidae, Dendropithecidae, and Proconsulidae are identified as successively more derived monophyletic clades. A monophyletic Oreopithecidae clade containing Oreopithecus and the nyanzapithecines is also well supported within Hominoidea. However, the positions of Pliopithecidae and Oreopithecidae are strongly influenced by the morphology preserved within single species in these clades. This demonstrates both the importance of comprehensive taxonomic sampling and the impact of missing data on phylogenetic results. The analysis also reveals that suspensory adaptations documented in living apes appeared independently in four hominoid clades (Pliopithecidae, Oreopithecidae, Hylobatidae, and Hominidae). This result is realized through the large taxon sampling in the analysis and demonstrate that the homoplastic character states in these taxa are expressed differently among clades. Finally, a general perspective on catarrhine evolution emphasizes that the appearance of the ancestral hominin cannot be properly interpreted without making reference to the entire Miocene ape radiation.