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and frequently-occurring marine macrofossil groups of the past 100+ million years worldwide. From their apparent origin in central Tethys in the late Jurassic they spread across most of the world’s oceans by the Late Cretaceous. They suffered substantial extinction at the K-Pg but diversified quickly thereafter, and they were present on every continent during the Paleogene. The record of their diversity, abundance, and morphology during the Cenozoic has become clearer due to recent studies of body size, molecular phylogenetic analysis, and systematic treatments of Paleogene, Miocene, and Plio-Pleistocene fossils from the Western Atlantic region (southeastern North America, the Caribbean, Central America, and northern South America). A database (still a work in progress) of more than 230 described species from this region shows turritellid diversity of more than 20 species in the Paleocene, a low of fewer than 10 in the early Eocene, a peak of more than 80 in the Miocene, a decline to around 20 in the Pliocene, and a decline to only 4 species in the central Western Atlantic today. Diversity within single formations shows a slightly different pattern, with highs of 11–16 species in the Late Miocene of Colombia and 18 species in the Late Pliocene Pinecrest Sand of Florida. Overall abundance has also declined, with turritellid-dominated assemblages common across the region throughout the Cenozoic, but limited today to only small areas of northern Venezuela. Higher taxonomic assignments of fossil and Recent turritellids and their phylogenetic relationships are still poorly known (and are likely to remain so for many species), but recent molecular data and systematic work on fossil turritellids indicate that several clades (e.g., Torcula) persisted in the region throughout the Cenozoic, while other groups which became significant likely appeared in the Miocene, including Vermicularia and Caviturritella. A common pattern in all of this change is correlation with likely patterns of primary productivity. Hyperdiverse assemblages and high regional diversity of turritellids appear to occur at times and places of high productivity, frequently in association with upwelling or significant terrestrial runoff, and patterns of extinction (temporal and geographic) correlate with declines in productivity. Funding source: NSF DEB 2225014 

Turritellid evolution represents a microcosm of large-scale patterns of molluscan evolution during the Cenozoic observed across the region. Additionally, isotopic studies of fast-growing turritellids and other gastropods have been important for documenting changing environment including the history of nutrient conditions associated with upwelling and different patterns of seasonal rainfall distribution across the region. These studies have included data from Colombia, Florida, Panama and Venezuela, documenting paleoenvironmental conditions that were substantially different than modern oceanographic conditions. Aside from being substantially impacted by extinction and showing declines in abundance along with other suspension feeding taxa, turritellids also exhibited 1) a shift towards hard substrate and biogenic substrate associated taxa; 2) a shift away from planktotrophy as a larval feeding mode; and 3) a loss of large species in association with the decline of high productivity environments. While soft-substrate-associated turritellids declined in both diversity and ecological significance, the reef and hardground associated turritellid genus Vermicularia continued to diversify, and Vermicularia now represent half of all turritellid species in the western Atlantic, and the majority of turritellid species in Florida. Larval mode within turritellids shifted towards increased lecithotrophy, independently in deeply divergent lineages when comparing modern taxa, fossil assemblages, and modern eastern Pacific species. The decline of the generally large-bodied taxon Caviturritella in the western Atlantic, including both the extirpation of Caviturritella from Florida and the extinction of the largest ever turritellid gastropod, Caviturritella abrupta, mirrors observed losses of many large-bodied taxa and declines in body size observed in other lineages, especially bivalves. Funding source: BMA is supported by NSF DEB 2225014 to WDA and J. Hendricks. 

The Plio-Pleistocene Pinecrest beds (Tamiami Fm.) of southern Florida rank amongst the most species-rich assemblages known from the Cenozoic macrofossil record. The tropical to subtropical fauna of the Pinecrest beds includes hundreds of mollusk species and subspecies (perhaps over 1,000), as well as diverse corals, bryozoans, and vertebrates. Some elements of the Pinecrest fauna are extant, but most species went extinct during one or more extinction pulses early in the Pleistocene. There was significant species turnover, but perhaps limited overall change in biodiversity relative to the present. Characterization of biotic change during this interval is important for understanding the evolution of the modern molluscan fauna of the southeastern United States but is unfortunately stymied by two major confounding factors. First, there are no natural exposures of the Pinecrest, and detailed sections have only been exposed in now-flooded quarries near Sarasota, Florida. Most samples from these and other quarries and canal cuts come from spoil piles, which often mix shells from multiple time intervals and habitats, limiting stratigraphic and ecological resolution for occurrence records. Second, the mollusks of the Pinecrest have not been comprehensively treated systematically and some elements of the macrofauna have likely been taxonomically over-split, leading to confusion and wariness among researchers about using published records in analyses. Conversely, the micromollusk fauna (<5.5 mm) has been understudied and many new species await description. Refining our understanding of this major regional turnover event is dependent upon a stable taxonomic foundation and supporting specimen occurrence data. Current estimates of diversity from literature and museum datasets do not closely align. Literature from the mid 1990s suggest over 550 species of gastropods and 250 species of bivalves in the Pinecrest beds, but numerous species have been described subsequently, the majority in the gray literature. In contrast to published tallies, over 1,000 and 400 names have been applied, respectively, to Pinecrest gastropods and bivalves in the collections the Florida Museum of Natural History, representing 140 families. Over 280 micromollusk species may also be present in the Pinecrest fauna. We have begun a project to comprehensively refine and substantiate these estimates of biodiversity to better characterize the Plio-Pleistocene turnover event(s) that led to the establishment of the modern fauna. Funding source: This research is supported by NSF DEB 2225014.