Early guenon from the late Miocene Baynunah Formation, Abu Dhabi, with implications for cercopithecoid biogeography and evolution.

A newly discovered fossil monkey (AUH 1321) from the Baynunah Formation, Emirate of Abu Dhabi, United Arab Emirates, is important in a number of distinct ways. At ∼ 6.5-8.0 Ma, it represents the earliest known member of the primate subfamily Cercopithecinae found outside of Africa, and it may also be the earliest cercopithecine in the fossil record. In addition, the fossil appears to represent the earliest member of the cercopithecine tribe Cercopithecini (guenons) to be found anywhere, adding between 2 and 3.5 million y (∼ 50-70%) to the previous first-appearance datum of the crown guenon clade. It is the only guenon--fossil or extant--known outside the continent of Africa, and it is only the second fossil monkey specimen so far found in the whole of Arabia. This discovery suggests that identifiable crown guenons extend back into the Miocene epoch, thereby refuting hypotheses that they are a recent radiation first appearing in the Pliocene or Pleistocene. Finally, the new monkey is a member of a unique fauna that had dispersed from Africa and southern Asia into Arabia by this time, suggesting that the Arabian Peninsula was a potential filter for cross-continental faunal exchange. Thus, the presence of early cercopithecines on the Arabian Peninsula during the late Miocene reinforces the probability of a cercopithecoid dispersal route out of Africa through southwest Asia before Messinian dispersal routes over the Mediterranean Basin or Straits of Gibraltar.