It has unattractive brown stains, is just a few millimetres across and part is broken off.
But a fossilised tooth from Abu Dhabi has yielded fascinating insights into the U.A.E. environment of millions of years ago, and indicated how monkeys may have dispersed from Africa.
Found in 2009 but only described in full in a scientific paper published this week, "AUH 1321” is just the second piece of fossil evidence of monkeys in Arabia.
It was found in the Baynunah Formation in Al Gharbia and is the subject of a paper in Proceedings of the National Academy of Sciences of the United States of America.
When the monkey was alive, between 6.5 million and 8 million years ago, what is now Abu Dhabi emirate was lush and green, and the fossil record shows it was home to big cats, ostrich-like birds and animals closely related to giraffes.
Crests running across the front and back of the tooth indicated it may have come from a monkey.
Careful measurements of other fossilised teeth in museums, coupled with statistical analysis, confirmed it probably came from a guenon, which is a member of the circopithecini tribe of "old world” monkeys.
Prof Christopher Gilbert, an assistant professor in the department of anthropology at Hunter College in New York and the lead author of the new paper, said it was "extremely interesting and a nice surprise” that the tooth was from a guenon.
That was not least because today these animals are restricted to Africa. Factors such as size ruled out other circopithecines, such as baboons and macaques.
"Guenons have distinctively shaped teeth that are usually narrower than are found in macaques and baboons,” said Prof Gilbert.
A key point of interest of the study is what it says about how monkeys may have travelled out of Africa into Eurasia.
Some researchers have suggested the creatures made this geographical leap in a period called the Messinian Salinity Crisis, between 5.96 million and 5.3 million years ago, when the Mediterranean Sea partly or completely dried up.
But the discovery of the fossil tooth indicates circopithecines could have used Arabia as a staging post to Eurasia well before the Messinian event. Other circopithecines are today found outside Africa, even if guenons are not.
"The Arabian Peninsula is a natural route for animals to go from Africa to Eurasia, [but] there's never been much evidence for that,” said Dr Faysal Bibi from Berlin's Natural History Museum, the second author of the paper and the person who saw the tooth in the sand.
"This find in Abu Dhabi really hits home that … African monkeys were living in the Arabian Peninsula, so from there could have colonised parts of Asia.”
The tooth is also interesting, he said, because the guenons had left behind an especially sparse fossil record, with "just a handful of specimens from Africa”.
"It's a discovery of a group of monkeys miles and miles away from where we would expect to find them today or from the fossil record,” said Dr Bibi.
Although scientists have identified the tooth as coming from a guenon, they are unsure whether the animal belonged to a new species or not.
With the only other monkey fossil discovered in Arabia, a canine tooth found in 1989, researchers were unable to pinpoint the type of monkey from which it came, since canine teeth yield less information than molars.
The other authors of this week's paper are Prof Andrew Hill, the J Clayton Stephenson Professor of Anthropology at Yale University, where the tooth is being kept, and Dr Mark Beech, head of coastal heritage and palaeontology in the Historic Environment Department at Abu Dhabi Tourism and Culture Authority.
Dr Beech said there were many other interesting finds from the Baynunah Formation that scientists were hoping to describe in due course.
"Some of the most interesting fossil discoveries waiting still to be analysed include an almost complete crocodile skull,” he said, adding that various hippopotamus bones had also been found.
Preliminary details of the fossilised monkey tooth were outlined late last year at a science conference, but this week's paper is the first to give a full description of the find.
Source: The National