INFLUENCE OF GEOGRAPHIC RANGE ON TAXONOMIC SURVIVORSHIP: COMPARISON OF ANALYSES AT DIFFERENT HIERARCHICAL LEVELS

Most marine animal genera are known from a single species within a narrow paleogeographic range during their stage of first appearance, and fail to persist beyond the first stage. Past work demonstrates that species richness and genus geographic range are positively correlated with survival past the first stage, and geographic range continues to influence survival thereafter. These relationships hold when genera are aggregated across the Phanerozoic, and within the Paleozoic and Cenozoic. Curiously, however, recent research demonstrates that geographic range does not influence survival past the first stage for genera first appearing in the Mesozoic, although those that do persist subsequently show the expected influence of geographic range.

We further examined the selectivity of Mesozoic marine animal survival spatially, temporally, and taxonomically using data from The Paleobiology Database (paleobiodb.org) . We found no support for differential survivorship regionally, and patterns within taxonomic groups appear more influential than overarching temporal patterns. Within certain classes (Ostracoda, Rhynchonellata, Anthozoa), geographic range strongly influences genus survival. For other classes, where selectivity is not apparent, more complex relationships sometimes exist at lower taxonomic levels. Some bivalve orders, for example, show strong selectivity, others weak, and pectinids show some evidence of the opposite effect, with surviving genera having smaller geographic ranges. In contrast, ammonoid cephalopod superfamilies, which generally have very high turnover rates, contain widespread genera that do not survive past their first stage. The few exceptions (Ancylocerataceae, Haplocerataceae, Turrilitaceae, Desmocerataceae, Phyllocerataceae) have genera surviving in greater proportions, rivaling nautiloids and belemnites, while maintaining vast geographic ranges. The abundance, diversity, and unusual survivorship selectivity of cephalopods strongly influence apparent selectivity when Mesozoic patterns for all groups are considered in aggregate, and help account for the aforementioned contrast with Paleozoic and Cenozoic selectivity.