Fossil links humans and monkeys
The primate had some features that are shared by Old World monkeys and apes
Researchers have discovered the skull of a 29 million-year-old animal that could be a common ancestor of Old World monkeys and apes, including humans.
It indicates that apes and Old World monkeys diverged millions of years later than previously thought, say the scientists.
The discovery was made in Saudi Arabia by researchers from the University of Michigan.
They described the primate, Saadanius hijazensis, in the journal Nature.
Dr William Sanders from the University of Michigan, who led the research, said this was "an extraordinary find".
The skull of this previously unknown species had some features that are shared by Old World monkeys and apes, including humans, today
"Saadanius is close to a group that eventually led to us," said Dr Sanders.
"If we knew something about the time period and the condition this animal was living in, we might be able to discover what brought about the changes that led to [the evolution of] apes and humans".
Dr Sanders explained that Saadanius might even have been the common ancestor that linked humans to Old World Monkeys.
"But there could have been a suite of creatures at the time that were very similar and one of them became our ancestor," he said. "We need to get out in the field and get more data before making bigger claims."
The fossilised remains indicate that the primate looked very much like a modern new world monkey, such as a capuchin. But it was probably slightly larger - about the size of a gibbon.
It would have used all four limbs to run around in the trees. When resting, the scientists say, it probably lay in the trees rather than sitting upright on the ground.
The discovery suggests that the divergence of apes and Old World monkeys happened much later than the 30-35 million years ago that genetic studies have suggested.
The new date, of 29 million years ago, fits more closely with what the researchers would have expected and is not surprising from a palaeontological point of view.
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Researchers have unearthed a new fossil  that they think may be closely related to the common ancestor of  and , collectively known as  primates. Paleontologist Iyad Zalmout of the  discovered the new species, '''' near  in ; the discovery gives new insights into .

The specimen, a partial skull, dates to the , approximately 29 to 28 million years ago, and exhibits puncture wounds from a large predator that may have killed it.  ''Saadanius'' is thought to have been a tree-dweller and lived at a time when the  had not yet split away from the African continent, forming the .  The discovery may help resolve the dating of the split between Old World monkeys and apes.   have traditionally dated the divergence to between 25 and 23 million years ago, based on early fossils of the two groups.  Genetic studies, however, date it to between 30 to 35 million years ago.

Although ''Saadanius'' shares some features with living catarrhine primates, such as a bony ear tube, called an , it also possesses other features more common in the fossils of primitive or  catarrhines, from which Old World monkeys and apes did not evolve.  These basal features include a longer face and the lack of a .