PATTERNS & TIMESCALES OF EXTINCTION & RECOVERY IN TURRITELLID GASTROPODS ACROSS THE K-PG (MAASTRICHTIAN-DANIAN) IN THE U.S. GULF & ATLANTIC COASTAL PLAINS

Turritellid gastropods are abundant and diverse constituents of benthic marine assemblages of Late Cretaceous and Early Paleocene age worldwide, including in the U.S. Gulf and Atlantic Coastal Plains (CP). Their macroevolutionary and macroecological patterns across the K-Pg boundary, however, are paradoxical. More than 20 species are cumulatively recorded from the late Maastrichtian and early Danian in the CP, yet none are known to span the K-Pg boundary itself – a finding consistent with global records of near-total species-level extinction in the family during this mass extinction. The geologically rapid recovery of global and CP turritellid diversity suggests, however, that multiple lineages must have survived the mass extinction, and this is supported by recent phylogenetic investigation of CP species which indicates that three or more such lineages likely survived in the CP region alone. Furthermore, these early Paleocene taxa closely resemble their late Cretaceous ancestors in community abundance and autecology.

A new analysis seeks to elucidate the full scope of turritellid ecologic and taxonomic change across the K-Pg in the CP at sub-stage resolution. By investigating patterns of extinction and recovery, we aim to uncover the macroevolutionary and macroecological impact of the K-Pg on this family of gastropods which, otherwise, does not broadly seem to have been impacted (on multi-million-year timescales) by the event. Within a temporally constrained phylogenetic framework, preliminary observations suggest that multiple surviving lineages underwent range fragmentation, offering a possible explanation for increased species richness in the early Paleocene: geographically isolated Danian populations exhibited higher speciation rates than their Maastrichtian ancestors. Changes in body size and larval ecology between and among clades also suggest that not all of the surviving turritellid lineages recovered from the K-Pg in the same way.