Wednesday 16 June 2010

Prehistoric mammal hair found in Cretaceous amber

Palaeontologists have discovered two mammal hairs encased in 100 million-year-old amber. While older 2D fossilised hairs are known, those preserved in the amber are the oldest 3D specimens known. The hairs, found alongside a fly pupa in amber uncovered in southwest France, are remarkably similar to hair found on modern mammals.

That implies that the shape and structure of mammal hair has remained unchanged over a vast period of time. "We have 2D hair imprints as early as the Middle Jurassic," says Dr Romain Vullo of the University of Rennes, France, who discovered the hair. The Jurassic Period lasted from 200 to 145 millions of years ago, followed by the Cretaceous Period which lasted to 65 million years ago.

"However, carbonised hair provides much less information about the structure than a 3D hair preserved in amber," says Dr Vullo. "Our specimens are the oldest known hair specimens in which we can observe the cuticular structure." Dr Vullo and Professor Didier Neraudeau identified the hairs, which were initially found by colleague Dr Vincent Girard in amber he was examining for microorganisms.

Details are published in the journal Naturwissenschaften.

The piece of amber, which is fossilised tree resin, was found in the Font-de-Benon quarry at Archingeay-Les Nouillers in Charente-Maritime, southwest France.

Dead or hungry?

The first hair fragment is 2.4mm long and 32 to 48 micrometres wide, while the second is just 0.6mm long and 49 to 78 micrometres wide. A close analysis of the hairs showed they have a very similar cuticular structure to those of hair or fur carried by modern mammals. The identity of the animal that shed the hair is not known. Four teeth of a primitive marsupial called Arcantiodelphys have been found in the quarry, above the layer in which the amber was found. "The more parsimonious hypothesis is to consider that the hair from the amber belong to this animal, or a closely related form," Dr Vullo told the BBC. As to how the hair became encased in amber, the researchers say there are three possibilities. Either amber swamped part of an animal's corpse, an idea that is supported by the fly pupa found alongside the mammal hairs, as a fly may have laid its eggs into the carcass of the dead animal.

Or the hair was lost by a living animal which brushed past the resin, perhaps by a tree-living (arboreal) species.
Or the hair was lost in a similar manner by a mammal that came to feed on insects trapped in the resin, which later fossilised into amber.

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