GSA Today
Volume 19, Number 4 (April/May 2009)

About the cover:
Shell bed with trilobites, brachiopods, tabulate corals, and gastropods from the middle Middle Cybele member, Jupiter formation (Early Silurian), Anticosti Island, Canada. Photo by Axel Uunnecke. See "Understanding the Great Ordovician Biodiversification Event (GOBE): Influences of paleogeography, paleoclimate, or paleoecology?" by thomas Servais et al., p. 4-10

© The Geological Society of America, Inc.