terça-feira, 14 de setembro de 2010

Lemur-like fossil gives clues to primate evolution

19 May 2009

A 47-million-year-old fossil of a lemur-like creature has given scientists an insight into the evolution of early primates, scientists at the University of Michigan report in the journal PLoS (Public Library of Science) today.

The exceptionally well-preserved fossil belongs to an extinct 9 or 10-month-old female primitive primate, called Darwinius masillae.

The specimen was unearthed from the Messel Pit near Darmstadt in Germany and is the most complete primate fossil to have been found.

It shows a very early stage in primate evolution, soon after the common ancestor of tarsiers, monkeys, apes and humans, branched off the evolutionary tree away from lemurs and lorises.

'The key significance of this exciting new fossil is that it is so complete,' says Dr Jerry Hooker, fossil mammal expert at the Natural History Museum.

'Fossil primates are notorious for being incomplete and the source of much discussion and debate, because they often consist only of isolated teeth or bones whose association is uncertain.'

Distant relations

The animal belongs to the extinct superfamily Adapoidea, members of which were previously thought to be distant relatives of living lemurs and lorises.

The team says that the new fossil shows this extinct primate group is more closely related to other primates, known as haplorhines, which includes tarsiers, monkeys, apes and ourselves.

Like a lemur?

Darwinius masillae lived during the period of Earth’s history called the Eocene. It was the size of a small monkey and looked similar to a lemur but with a shorter snout and shorter hind limbs.

It was arboreal, meaning it was a specialised tree climber, and able to grip narrow branches with all four feet.

However, it lacked some key lemur characteristics such as a tooth comb and a particular structure of the ankle.

Well-preserved fossil

The fossil is exceptionally well-preserved and even shows fur imprints and the stomach contents from its last meal.

The specimen also shows some of the more advanced characteristics of all other primates (the haplorhines) like aspects of the skull, teeth and feet.

Importance of specimen
Skull of an extinct giant lemur - 1 of 9 million specimens looked after in Museum fossil collection

Skull of an extinct giant lemur - one of 9 million specimens looked after in the Museum fossil collection.

Dr Hooker studies some of the 9 million fossils at the Natural History Museum and explains the importance of this new fossil.

‘This new find tells us what the entire skeleton of an early haplorhine was like, right up to the tips of its fingers and toes.’

‘It will set us on a firmer track towards solving currently more intractable questions like the nature of primate origins before there is a fossil record.’

‘Being so complete, it will form a standard, with which more fragmentary specimens will need to be compared.’

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