A skull part of Saadanius hijazensi found in February 2009 during a joint field expedition of the Saudi Geological Survey and the University of Michigan. The skull with highly visible teeth and palatal bone was enclosed in iron-rich debris in the middle part of the Shumaysi Formation. Image: Iyad S. Zalmout, University of Michigan Museum of Paleontology, 2009
Read aloud A newly discovered monkey species was one of the last common ancestors of the whitewashed Old World monkeys and the human-like monkeys. This is proven by skull parts found by an American-Saudi Arabian research team in deposits of the Shumaysi Formation in Saudi Arabia. According to the 28 to 29 million year old fossil remains of a so-called Old World monkeys of medium size. Anatomical and genetic analyzes revealed similarities with both the human-like monkeys? to which, according to biological systematics, man also belongs? as well as with the tailed Old World monkeys. Thus, the splitting into these two families took place much later than previously assumed. In the study of human evolution, the question is controversial, when the Old World monkeys, ie the monkeys of Eurasia and Africa, in the two primate families of the tailed Old World monkeys and the human-like monkeys? Apes and humans? have split up. Previous estimates from scientists date back to about 30 to 35 million years ago. In rock strata from the geological era of the Oligocene 30 to 23 million years ago, however, only a few fossils could be found, which gave information about the nature and the last appearance of common ancestors.

The skull parts found now were located in the middle layer of the so-called Shumaysi Formation in western Saudi Arabia, which is about 28 to 29 million years old. The skull pieces had characteristics that do not fit into any known Old World monkey species: Thus, among other things, the teeth differ in size and shape from those of other species in addition to numerous other characteristics. The found specimen of Saadanius hijazensis, the name of the new primate, was male and weighed between 15 and 20 kilograms during his lifetime.

Thanks to modern genetic methods and the comparison of the skull features he was classified as a common ancestor of the human-like monkeys and the tailed old world monkeys. The cleavage of Old World monkeys into the two families can therefore have occurred at least 28 to 29 million years ago, as the middle deposits of the Shumaysi Formation, the scientists explain. The find also confirms that the evolution of Old World monkeys and thus also the origins of man are closely linked to the Afro-Arab region.

William Sanders (University of Michigan, Ann Arbor) et al .: Nature, vol. 466, no. 7304, doi: 10.1038 / nature09094 ddp / science.de? Thomas Neuenschwander advertisement

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