IMPROVED ESTIMATES OF PHANEROZOIC MARINE DIVERSITY

Although work continues, data collection by the marine invertebrate working group of the Paleobiology Database has progressed to the point where a base-line diversity curve for the entire Phanerozoic can be generated. Since the group's joint paper in 2001, 48 researchers from 14 institutions have worked to compile new data. The number of marine fossil collections has increased by 170%, and the number of taxonomic occurrences by 130%. The original data set included information on 82 countries, whereas the current total is 120. Members of the Database have published 16 papers related to the group's activities. Much work has been done on temporal gaps, in particular a long one between the Permian and mid-Jurassic. Our earlier main goal was to use sampling standardization to test for a marked increase in diversity through the Phanerozoic, but the new data make it possible to address a series of other questions. The data allow a higher standardized sampling level. Collections with overly broad spatial or stratigraphic scales may be excluded. Major paleoenvironmental and lithological categories may be analyzed separately. Trends in the proportional diversity of major groups may be assessed, as may the effects of including or excluding groups from diversity curves. A concern with our earlier analysis was possible undersampling in low latitudes during the Cretaceous and Cenozoic. The additional collection data and now-complete coordinate data make it possible to test for the effects of paleolatitude and spatial concentration of collections. In particular, it is possible to quantify paleolatitudinal diversity gradients by analyzing geographic areas separately. The data are indeed robust enough to demonstrate some gradients. Our data also allow us to assess major mass extinction events, some of which have been called into question recently by independent analyses. Our estimates of diversity will continue to improve as further collection-based faunal data are compiled and analyzed. We thank working group members S. Holland, D. Jablonski, T. Olszewski, and P. Wagner for their contribution of data and their intellectual input.