NEW AMBER DEPOSIT PROVIDES EVIDENCE OF EARLY PALEOGENE EXTINCTIONS, PALEOCLIMATES, AND PAST DISTRIBUTIONS

Abstract

AbstractA large, previously unstudied amber deposit in British Columbia dating from the Early to Middle Eocene (50−55 Ma) provides a noteworthy new source of terrestrial invertebrates and other life forms. This deposit contains what are likely the earliest unequivocal ants (members of the family Formicidae), including extinct representatives ofTechnomyrmexMayr 1872,LeptothoraxMayr 1855, andDolichoderusLund 1831. DiscoveringTechnomyrmexand a corydiinid cockroach, both of which are currently restricted to tropical regions, confirms earlier evidence of warm paleoclimates and past biogeographic distributions in the early Paleogene. Chemical analysis of the amber indicates that the source tree was an araucarian belonging to or near the genusAgathisSalisbury 1807, and demonstrates that this genus survived into the Tertiary in the Northern Hemisphere, since previous records revealedAgathisas a component only of the Cretaceous forests in North America. Comparing the Hat Creek fossil assemblages in this deposit with those from the well-studied western Canadian Late Cretaceous amber deposits offers a unique opportunity to study extinction and speciation events on both sides of the Cretaceous–Tertiary boundary.