Conversations about Phanerozoic Global Diversity

-The emergence of Phanerozoic global diversity as a central theme of investigation has resulted from a confluence of factors, including the assembly by several researchers of global taxonomic databases; the advent of computers, which permitted construction and analysis of global Phanerozoic diversity trajectories; and the recognition that Phanerozoic diversity trends are important bellwethers of the evolutionary processes that cause biotic transitions. Despite the enormous progress in the measurement and interpretation of Phanerozoic diversity over the past quarter century, much of which has been reported in Paleobiology, these studies have collectively generated at least as many new questions as they have answered-arguably the mark of an area of inquiry that continues to be vital. In this essay, I discuss several outstanding issues in the investigation of Phanerozoic diversity, ranging from the viability of literature-derived databases for investigating global diversity trends, to the biological significance of the myriad biotic transitions that have taken place throughout the IJhanerozoic. Arrlolii I . ~Willer. Departw7etzt of Geology, Post Office Box 210013, University of Cincinnati, Cincinnati, Ohio 45221-0013. E-mail: [email protected] Accepted: 22 June 2000 chard was curious to know what I thought of "Do these patterns compel me to b e l i m that the paper. My simple response was, "I liked bivalves and brachiopods have been locked hand it." to hand (or, foot to pedicle) in some sort of mortal This wasn't enough for Richard; he was not combat for the last 500 million years? M y angoing to let me off the hook with a polite reswer is no, not really. . . ." (Sepkoski 1996: p. sponse. So, he asked, "Yes, but what did you 242). think of it?" I paused for a moment, and said, again, "