The K/T event and infaunality; morphological and ecological patterns of extinction and recovery in veneroid bivalves

Although the causes of mass extinctions have been studied in detail, recoveries have received little attention until recently. In this study, I examine the influence of extinction versus recovery intervals on ecological patterns across the end-Cretaceous (K/T) event in veneroid bivalves. Systematic and stratigraphic data were collected for 140 subgenera of veneroids, ranging from the Late Cretaceous through Oligocene of North America and Europe. Morphological data were collected for 1236 specimens representing 101 subgenera. Extinction selectivity and differential recovery were assessed with respect to morphology, and by extension, burrowing ecology in these bivalves. Eighty-one percent of veneroid subgenera went extinct at the K/T and diversity did not return to preextinction levels until 12 million years later. Despite the severity of the K/T extinction, I found little evidence of morphological or ecological selectivity. The K/T recovery, in contrast, was strongly biased toward taxa with deep pallial sinuses (i.e., toward deeper burrowers). For veneroids, the morphological and ecological effects of the K/T event are not tied to the extinction itself, but to the recovery that followed. The K/T recovery initiated a trend toward deeper burrowing that helped to establish veneroids as one of the most abundant and successful groups of modern marine bivalves.