Monday, October 25, 2010

Early Eocene Amber from India

Biogeographic and evolutionary implications of a diverse paleobiota in amber from the early Eocene of India. 2010. J. Rust, et al. PNAS, Published online before print October 25.

David Grimaldi/AMNH
Bees, termites, spiders, and flies entombed in a newly-excavated amber deposit are challenging the assumption that India was an isolated island-continent in the Early Eocene, or 52-50 million years ago. Arthropods found in the Cambay deposit from western India are not unique—as would be expected on an island—but rather have close evolutionary relationships with fossils from other continents. The amber is also the oldest evidence of a tropical broadleaf rainforest in Asia.

Amber from broadleaf trees is rare in the fossil record until the Tertiary, or after the dinosaurs went extinct. It was during this era that flowering plants rather than conifers began to dominate forests and developed the ecosystem that still straddles the equator today. The new amber, and amber from Colombia that is 10 million years older, indicates that tropical forests are older than previously thought.

The amber has been chemically linked to Dipterocarpaceae, a family of hardwood trees that currently makes up 80 percent of the forest canopy in Southeast Asia. ossilized wood from this family was found as well, making this deposit the earliest record of these plants in India and showing that this family is nearly twice as old as was commonly believed. It most likely originated when portions of the southern supercontinent Gondwana were still connected. link