FISH DIVERSITY AND THE ROLE OF PREDATION IN MARINE REVOLUTIONS

Benthic predators, particularly fishes and other aquatic vertebrates, have been designated as key drivers of marine revolutions ever since the phenomenon was identified by Vermeij. Arms races between shell-crushing (durophagous) fishes and their benthic invertebrate prey are thought to cause increased diversity of form in the latter, as new defensive traits arise. Thus, specific revolutions (e.g. the Mesozoic and mid-Paleozoic) are hypothesized to coincide with the appearance of novel fish predators (teleost or jawed fishes, respectively) or predatory modes, which would constrain invertebrate diversification to specific intervals in time. Unfortunately, the taxonomic and morphological diversity of Paleozoic and Mesozoic durophagous fishes has rarely been studied specifically, particularly in a synoptic or quantitative fashion. As a result, the vertebrate aspects of these hypotheses remain largely untested. Here, we present results from the first set of compendia tracking the absolute and relative taxonomic diversity of durophagous ray-finned (Actinopterygii) and cartilaginous fishes (Chondrichthyes) through time. Because apparently static lineage diversity can mask functional novelty, we have tracked dental morphology of these fishes in order to measure relative disparity in each interval. Our analyses reveal whether various documented marine revolutions are indeed coincident with significant increases in predatory fish diversity or disparity, or whether other drivers should be sought out.