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Amber's Thousand Treasures

For the past several years, researchers at CNRS have been searching for small animals and other evidence from prehistory trapped in pieces of amber. Their latest discovery consists of feathers belonging to the ancestor of birds.

Though it may look like just the latest in a long series of exceptional finds, these prehistoric feathers embedded in a piece of amber strengthen the hypothesis that birds are in fact the descendants of dinosaurs. This recently published discovery adds to the number of surprising revelations that have come from amber, and shows that scientists are becoming more skilled at revealing its secrets, according to Didier Néraudeau, a professor at Rennes’ Geosciences laboratory.1 Along with Vincent Perrichot and André Nel, two of his colleagues at MNHN2 in Paris, Néraudeau is interested in an amber deposit he has known about for a long time since it is located behind his grandparents’ house in Charente. He has gathered large quantities of the 100 million-year-old fossilized resin. Of the 60 kg collected, 80% is completely opaque, but the analysis of the remaining 20%–which is translucent–has uncovered a micro-bestiary of organisms that were contemporaries of dinosaurs. The researchers discovered mites, worms, flies, ants, crustaceans–in total, 650 fossilized animals and a wide variety of plant species, all exceptionally well-preserved. “The number of mid-Cretaceous sites of this quality in the world can be counted on one hand,” Néraudeau enthuses.
His enthusiasm is not simply because the Charente amber makes it possible to inventory hundreds of extinct and undocumented species, but because major results have followed its discovery. Several months ago, Néraudeau and his colleagues published an article on the origin of ants. As he explains, “it was previously thought that ants appeared about 85 million years ago. We show, however, that not only were they already present 100 million years ago, but that they were already organized in castes. This indicates that the origin of these insects is more ancient still.”
The specialists have also discovered fossils of zodariidae, spiders whose modern descendants are predators of ants. This is evidence that this predator-prey pair was around before the Cretaceous-Tertiary event that led to the extinction of the non-feathered dinosaurs 65 million years ago. “This discovery proves that insects and their ecosystems were probably not perturbed by the crisis,” the paleontologist points out.
Lastly, the recently discovered feathers confirm what paleontologists already believed, namely that birds are distant relatives of one group of dinosaurs. Over the past few years, several sites in China had in fact revealed feathered dinosaur remains, supporting this hypothesis. Nevertheless, paleontologists are still looking for intermediate links between the most primitive feathers of the Chinese dinosaurs, similar to small filaments, and the modern feathers of birds. The Charente feathers are one of these links. “The feathers are composed of several barbs, meeting at their base to form a primitive version of the central shaft of modern feathers,” says Néraudeau. “This discovery further supports the idea that some dinosaurs gradually evolved into birds.”
And this rich influx of findings is not about to end. Indeed, since 2006 Paul Tafforeau, at the synchrotron facility in Grenoble (ESRF),3 uses a technique known as microtomography to image the interior of opaque amber. This technique shows that opaque amber also contains hundreds of small fossilized animals. “It took us four years of work to discover 650 inclusions in translucent amber, using conventional techniques,” says Néraudeau. “With the synchrotron, 350 new specimens were identified in a single session!”
Research has also started on bacteria, algae and fungi preserved in the amber. Furthermore, the scientists believe that the study of plant fossils will soon reveal information about the environment in which flowering plants originated. Was it an aquatic environment, and if so, was it fresh water? No answer has yet been found. As for air or water bubbles trapped in the fossilized resin, they may reveal precious information about ancient climate. Amber research holds much promise for a host of scientific disciplines.

Mathieu Grousson

Notes :

1. CNRS / Université de Rennes-1.
2. Muséum national d'Histoire naturelle.
3. European Synchrotron Radiation Facility.

Contacts :

Didier Néraudeau, Géosciences, Rennes.


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