First Fossil-bearing Amber Discovered In Western Amazonian Basin By American Museum Of Natural History Paleontologist And Colleagues

John Flynn excavating fossils from the upper lignite level at the amber locality, western Amazon

Credit: Pierre-Olivier Antoine

An international team of scientists, including an American Museum of Natural History paleontologist, has discovered the first pieces of fossil-bearing amber--preserving an exceptional diversity of insect, arachnid, and plant species--in the western Amazonian basin. The amber finding provides the first evidence that a great number of insect and spider species lived in this region and populated tropical equatorial environments during the middle Miocene Epoch, about 15 million years ago. Until now, fossil-bearing amber in South America has only been reported in Patagonia, eastern Brazil, and French Guyana. The new amber preserves a wide array of organisms, including insects, arachnids, algae, pollen, fungi, bacteria, and spores from more than 30 types of fungi and plants. Many of the spore forms and all of the arthropods (a group that includes insects, arachnids, and crustaceans) appear to be new to science. The remarkable diversity of the organisms and their ecological specializations suggest a tropical rain forest environment, indicating that modern types of ecosystems were already well-established by the Miocene in western Amazonia. Amber preserves delicate plant structures, soft-bodied animals, and microbes better than sediments, but even conventional fossils of most groups of animals living today are virtually unknown from the Amazon basin. Prior to discovery of this amber, little has been known about the history and evolution of land-dwelling insects, arachnids, and microbes of the past 65 million years in South America. The new finding is described in the journal Proceedings of the National Academy of Sciences by John J. Flynn, Chairman and Frick Curator in the Museum's Division of Paleontology, and colleagues including other principal authors Pierre-Olivier Antoine, Dario De Franceschi, and Andrel, all with the Centre National de la Recherche Scientifique (CNRS) in France, and Rodolfo Salas-Gismondi, of the Universidad Nacional Mayor de San Marcos, in Lima, Peru.

Small fly (Diptera: Phoridae [female]), trapped in an amber clast from the middle Miocene of the western Amazon. Living species of Phoridae are often found around decaying vegetable matter or animals. Ventral view, length ca. 1.2 mm.

Photograph by Dario De Franceschi (Mus National d'Histoire Naturelle, Paris)

"This discovery provides the first glimpse of the spectrum of soft-bodied organisms living in western Amazonia during the Miocene. Such forms are not often preserved in the fossil record," said Dr. Flynn. "We now have evidence that a high-biodiversity rain forest typical of modern ecosystems in the area was present here 12 to 15 million years ago."

The amber pieces, 3 large and 25 smaller ones, were hand-picked from rock layers exposed along the Amazon River in the western Amazon. The amber probably originated from a broad-leafed tree living in moist forest undergrowth. Researchers previously had noted finding rare amber debris in the area but had not reported fossils in it. The arthropods are unique but will require further phylogenetic study to determine their evolutionary relationships to known forms. The amber preserves an ecologically diverse array of arthropods, including parasitic bees or wasps; two flies that live in humid environments; beetles that might live in algae, fungi, or moss; three species of mites or ticks; two insects that live on the ground in humid environments; and an insect with aquatic larvae.

Other aspects of the rock layers in which the amber was found support the paleontological evidence for a tropical rain forest environment. The sediments preserve an abundance of unidentified coalified plant remains and fern spores typically associated with a forest. Previous geological studies also have indicated that the Miocene of this part of the western Amazonian Basin included a tropical rain forest along with swamps, plains, grasslands, bodies of water, and intermittent mangrove forests. The discovery of this fossiliferous amber will clarify understanding of the evolutionary history of the modern Amazonian biota, as well as the paleoecology of this area, which underwent drastic environmental changes throughout the Miocene.

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