ANN ARBOR, Mich.---When paleontologist Iyad Zalmout went looking for fossil whales and dinosaurs in Saudi Arabia, he never expected to come face-to-face with a significant, early primate fossil.
But the skull he stumbled upon provides new insights into what the last common ancestor of apes and monkeys may have looked like and when the two lineages went their separate ways.
Zalmout and colleagues at the University of Michigan and the Saudi Geological Survey describe and interpret the fossil in a paper published online July 15 in the journal Nature.
It is well known that Old World monkeys and apes share ancestry, but exactly when the two branches split from the common trunk has been unclear. Debates also have swirled around the question of what sort of facial structure the progenitor of apes and monkeys had.
Both lineages belong to the primate group known as catarrhines. The earliest catarrhines in the fossil record, creatures that were neither monkey nor ape, date back to the late Eocene to early Oligocene epochs, 35 to 30 million years ago. Later fossils, from around 23 million years ago, suggest the split had already occurred by that time. But few fossil catarrhines from the interval between 30 million to 23 million years ago have been found, making it difficult for scientists to know precisely when monkeys and apes became distinctly separate groups and what catarrhines looked like around the time of the split.
The new fossil catarrhine, Saadanius hijazensis, dates from 29 million to 28 million years ago and lacks the specialized features that distinguish modern apes and Old World monkeys, suggesting that the split had not yet occurred. The researchers' analysis of the fossil leads them to believe its physical features are much like those of the last common ancestor of Old World monkeys and apes.
Zalmout, a postdoctoral fellow working with U-M paleontologist Philip Gingerich, found the fossil in
|Contact: Nancy Ross-Flanigan|
University of Michigan