TRENDS IN DRILLING PREDATION AND PARASITISM ON ECHINOIDS DURING THE MESOZOIC MARINE REVOLUTION

The Mesozoic Marine Revolution (MMR), an ‘evolutionary arms race’ between predators and prey in marine ecosystems, predicts an increase in intensity of biotic interactions through time. A substantial line of evidence used to assess the MMR is derived from drill holes produced by drilling predators that prey on mollusks. In contrast, biotic interactions affecting another major group of marine invertebrates, the echinoids, have received much less attention. Predatory cassid and parasitic eulimid gastropods are known to produce drill holes in living echinoids. However, these biotic interactions are relatively understudied in the fossil record. Here, we examine combined data from new field sampling efforts, surveys of museum specimens, and the paleoecological literature to elucidate macroevolutionary and macroecological trends in the intensity of trace-producing predation and parasitism on echinoid prey/hosts. Preliminary analyses focused on changes in drill-hole frequencies during important evolutionary events in the history of the tracemakers and their echinoid targets. The two key events include the diversification of cassids and eulimids in the early Cenozoic and the radiation of infaunal echinoids in the Cretaceous. Preliminary analyses indicated a near absence of drill-hole occurrences in the Early Cretaceous and a gradual increase in drill-hole frequencies through the Late Cretaceous and Paleogene following the appearance of cassids and eulimids in the fossil record. The earliest significant increase in drilling frequency occurred in the Eocene, coincident with a well-documented diversification of cassids and eulimids. The Eocene increase in drilling intensity on echinoids stands in contrast with the timing of the rise of drilling on mollusks, already well underway by the Late Cretaceous. Additionally, drilling intensification in echinoids occurred long after the evolution and radiation of infaunal echinoids, which took place in the Cretaceous as well. These preliminary trends imply that the increase in drilling predation and parasitism on echinoids notably postdates the infaunalization of echinoids and the rise of drilling predation on mollusks, suggesting that evolutionary pressures other than predation by drilling organisms may have driven major evolutionary trends in echinoids.