灵长类的化石记录很稀少，仍然存在实质性的缺口。其中一个缺口是“旧世界”的猴子与“新世界”高等灵长类内的类人猿和人类的分化。这种分化以前仅限于“非洲-阿拉伯大陆”的渐新世，但在沙特西北一个新的、处在进化树根部的狭鼻猿的发现缩小了这个缺口。

沙特发现的这个材料来自距今约2800万年前的渐新世中期，它的狭鼻猿分化特征非常少，说明“旧世界”的猴子与“新世界”的类人猿之间的分化发生在那个时期之后。本期封面所示为头盖骨的前部，其犬齿和上颚宽臼齿都在原处。头盖骨的大小表明这是一个中等大小的灵长类，体重在15公斤和20公斤之间。

原文出处：
 
Nature doi:10.1038/nature09094

New Oligocene primate from Saudi Arabia and the divergence of apes and Old World monkeys
Iyad S. Zalmout1, 2；William J. Sanders1, 3；Laura M. MacLatchy1, 3；Gregg F. Gunnell1；Yahya A. Al-Mufarreh4；Mohammad A. Ali4；Abdul-Azziz H. Nasser4；Abdu M. Al-Masari4；Salih A. Al-Sobhi4；Ayman O. Nadhra4；Adel H. Matari4；Jeffrey A. Wilson1, 2；Philip D. Gingerich1, 2, 3

It is widely understood that Hominoidea (apes and humans) and Cercopithecoidea (Old World monkeys) have a common ancestry as Catarrhini deeply rooted in Afro-Arabia1, 2, 3, 4. The oldest stem Catarrhini in the fossil record are Propliopithecoidea, known from the late Eocene to early Oligocene epochs (roughly 35–30?Myr ago) of Egypt, Oman and possibly Angola5, 6, 7, 8, 9, 10. Genome-based estimates for divergence of hominoids and cercopithecoids range into the early Oligocene11; however, the mid-to-late Oligocene interval from 30 to 23?Myr ago has yielded little fossil evidence documenting the morphology of the last common ancestor of hominoids and cercopithecoids, the timing of their divergence, or the relationship of early stem and crown catarrhines. Here we describe the partial cranium of a new medium-sized (about 15–20?kg) fossil catarrhine, Saadanius hijazensis, dated to 29–28?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 29–28 and 24 Myr ago.