Mammalian Hair Fragments found in Cretaceous Amber
Scientists from France have reported the discovery of preserved mammal hair in a piece of amber that dates from the Cretaceous period. These two tiny fragments of hair are the oldest three-dimensional mammalian hair known. Hopefully, the mammalian hair will provide more data on the evolution of mammals than other fossil remains, the amber (fossilised tree resin), has preserved the hair in three dimensions and scientists are confident that they can obtain more information from this sort of fossil than from conventional body fossils that tend to be two-dimensional.
The pair of tiny hairs, found alongside a fly pupa in amber were discovered in a quarry in southwest France. The hair is remarkably similar to hair found on modern, extant mammals. The scientists state that this evidence suggests that the shape and structure of that most mammalian of characteristics – hair, has remained unchanged over a vast period of time. Mammalian hair’s primary function is to help insulate these endothermic (warm-blooded) animals. Since the first types of mammals to evolve were mouse-like creatures, evolving an effective form of insulation would have been very important to them, especially since they probably filled a nocturnal niche in the Mesozoic.
Dr Romain Vullo of the University of Rennes (France) who made the hair discovery stated:
“We have 2-D hair imprints as early as the Middle Jurassic, however, carbonised hair provides much less information about the structure than a 3-D hair preserved in amber.”
The picture shows a close up of the mammalian hair, a strand can be viewed in the centre of the picture, it is lying in a horizontal position, the circular texture can be made out.
Dr Vullo went on to add:
“Our specimens are the oldest known hair specimens in which we can observe the circular structure”.
Dr Vullo and Professor Didier Neraudeau identified the two hairs, they had been initially found by colleague Dr Vincent Girard as he examined the amber for traces of micro-fossils.
The piece of amber was found in the Font-de-Benon quarry at Archingeay-Les Nouillers in Charente-Maritime (southwest France). The details of the French team’s discovery are reported in the scientific journal “Naturwissenschaften”.
The largest of the hair fragments is 2.4 mm long, it measures 32 to 48 micrometres wide, whilst the second is just 0.6mm long and 49 to 78 micrometres wide. In comparison, a strand of human hair is about 100 micrometres wide.
It is not known from which animal the hair samples are from, however, fossil teeth from a small marsupial mammal, Arcantiodelphys have been found in slightly earlier strata in a zone above the layer in which the amber nodule was found.
The identity of the animal that shed the hair is not known. It is difficult to assign a genus or even a mammalian family to the hair sample.
Three theories have been put forward to explain how the hair got stuck in the tree resin in the first place. Firstly, tree resin could have swamped part of a little mammal’s corpse. This ideas is supported by the presence of the fly pupa found alongside the mammal hairs, as a fly may have laid its eggs into the carcase of the dead animal.
Secondly, the hair may have been lost by a living animal which brushed past the sticky resin, perhaps by a tree-living (arboreal) species. Thirdly, the hair could have been lost by a mammal that came to feed on insects trapped in the resin, which later fossilised into amber.
It is unlikely that the scientists will ever find evidence to support one of these theories, or indeed to explain the presence of the hair trapped in the tree resin. However, the beautifully preserved hair will permit the team to learn a little more about the mammalian fauna that scurried about under the noses of the dinosaurs of the Cretaceous.
The evidence suggests that mammalian hair once it evolved has changed very little over millions of years, this is an example of “evolutionary stasis”.
To read more about an aspect of evolutionary stasis: Pelicans have had their pouches for 30 million years.