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Nature 15 July 2010 V. 466, pp. 295-406, S1-S22
English | pdf | 57.7  mb | 134 pages

Cover story: The fossil cranium of a new stem catarrhine from western Saudi Arabia allows palaeontologists to place a more accurate date than previously possible on the divergence of cercopithecoids (Old World monkeys) and hominoids (apes and humans) within Old World higher primates (Catarrhini). The new specimen dates to the mid-Oligocene, around 29 million to 28 million years ago, and has no crown catarrhine specializations other than the presence of a tubular ectotympanic, suggesting that the divergence of Old World monkeys and hominoids happened after that date. The cover shows the anterior view of the cranium, which has its lateral incisors, canines and broad molars in situ. The size of the cranium indicates a medium-sized primate, between 15 and 20 kilograms in body mass.
Here we describe the partial cranium of a new medium-sized (about 15??0 kg) fossil catarrhine, Saadanius hijazensis, dated to 29??8 Myr ago. Comparative anatomy and cladistic analysis shows that Saadanius is an advanced stem catarrhine close to the base of the hominoid–cercopithecoid clade. Saadanius is important for assessing competing hypotheses about the ancestral morphotype for crown catarrhines1, 12, 13, 14, early catarrhine phylogeny12, 15 and the age of hominoid–cercopithecoid divergence11. Saadanius has a tubular ectotympanic but lacks synapomorphies of either group of crown Catarrhini, and we infer that the hominoid–cercopithecoid split happened later, between 29??8 and 24 Myr ago.
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