Meeting Abstract

64.2  Tuesday, Jan. 6  The fossil neogastropod genus Bruclarkia in the Eastern Pacific: investigations of its endemism and speciation VENDETTI, J.E.; Univeristy of California, Berkeley jannv@berkeley.edu

The extinct buccinid gastropod genus Bruclarkia Trask in Stewart, 1927, includes thirteen species from the Paleogene and Neogene of California, Oregon, Washington, Vancouver Island, and Alaska. Genera in the family Buccinidae are common and abundant throughout the active margin of the Pacific Rim, and Bruclarkia is noteworthy in that it is a genus endemic to the East Pacific. This genus first appears during the Eocene in the Keasey Formation of Oregon and is last seen in the Oregon Astoria Formation of the middle Miocene. A radiation of Bruclarkia species occurred in the early Oligocene after a local extinction near the Eocene/Oligocene boundary in the Pacific Northwest wiped out more than ninety percent of mollusk species. The genus went extinct about 20 million years later, with no Bruclarkia species giving rise to any extant neogastropod. In this study, more than 200 Bruclarkia fossils were analyzed and seventeen character states of shell morphology were identified. By polarizing morphological characters and correlating species with stratigraphic data, a suite of derived Bruclarkia shell characters was identified. To further elucidate the evolutionary history of this genus, the original and steinkern-preserved protoconchs of Bruclarkia were examined to infer larval developmental mode, and the shell morphology associations with substrate and inferred depth.