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1. Systematics and phylogeny of Plio-Pleistocene species of Turritellidae (Gastropoda) from Florida and the Atlantic Coastal Plain

   Friend, Dana S.; Anderson, Brendan M.; Altier, E.; Petsios, E.; Portell, R. W.; Allmon, W. D. (April 2023, Bulletins of American paleontology)

   Hendricks, Jonathan R. (Ed.)

   Turritellid gastropods are among the most widespread, abundant, and diverse mollusks in Plio-Pleistocene deposits of the Atlantic coastal plain and Florida, with at least 46 species and subspecies described over almost two centuries. Yet the systematic status of these common fossil species and their phylogenetic relationships—to each other and to turritellids living today in the western Atlantic—have never been investigated in detail. We make use of recent molecular phylogenetic work on living turritellids and new analyses of shell characters to review the group from this time interval to the present in a comprehensive phylogenetic analysis and assessment of their evolutionary history in the region. We conclude that 20 fossil and two Recent species are valid. Four of these species are placed in the genus Torcula Gray, 1847; five in Caviturritella new genus, and eleven in “Turritella” sensu lato. We identify Torcula perattenuata as the likely direct ancestor of one of the two turritellid species living today off the southeastern U.S. coast, Torcula exoleta, and we elucidate the fossil record of the other extant species, “Turritella” perexilis (senior synonym of Turritella acropora). We show that Caviturritella was extirpated from the United States Gulf and Atlantic coastal plains in the Early Pleistocene but is still represented in the western Atlantic by the living species C. variegata in the southern Caribbean. We also present the first detailed treatment of Plio-Pleistocene turritellid fossils from Georgia. Our analysis shows that the Plio-Pleistocene Pinecrest beds of Florida contain 18 co-occurring turritellid species, which is the highest turritellid species diversity in one formation known in the fossil record. 

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2. Macroevolutionary and macroecological trends in Turritellidae in the western Atlantic Neogene-recent: insights from an abundant, well-studied taxon

   Anderson, BM; Allmon, WD (July 2024, Museum of Paleontology, The University of Michigan; University of Michigan Papers on Paleontology)

   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. 

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3. Plio-Pleistocene stratigraphy, paleoenvironments, and sea-level history at Florida Shell Quarry, Charlotte County, Florida, U.S.A.

   https://doi.org/10.2110/jsr.2024.090  

   Gomes, Lucas D; Petersen, Sierra V; Portell, Roger W; Riemersma, Peter E (April 2025, Journal of Sedimentary Research)

   ABSTRACT Plio-Pleistocene sediments from the southwestern Florida Peninsula contain an extraordinary density and diversity of marine mollusk and vertebrate fossils which, collectively, document major faunal shifts on the Florida Platform through a period of profound environmental change. Systematic study of these fossil assemblages and the environments in which they lived has been limited, however, by: i) a lack of outcrop sections spanning the full Plio-Pleistocene stratigraphy of the region and ii) major uncertainties in correlation between previous study sites due to extreme lateral variability in coastal paleoenvironments. Here, we describe a new stratigraphic section from Florida Shell Quarry in Charlotte County, Florida, which contains fossil-rich deposits of each major Plio-Pleistocene unit in the area (the Tamiami, Caloosahatchee, Bermont, and Fort Thompson formations). Bulk sediment samples collected from 22 horizons were used to broadly characterize stratigraphic variations in lithology and faunal content. Predation intensity was estimated from drill-hole frequency among populations of the bivalve Chione spp. While all studied formations were mainly deposited under marine conditions, both lithologic and faunal facies shifts within the Caloosahatchee and Bermont units indicate periods of pronounced freshwater influence. Faunal diversity is relatively high in the Tamiami, Caloosahatchee, and Bermont units but declines in the Fort Thompson. Similarly, predation intensity is high in the Caloosahatchee and Bermont units but lower in the Fort Thompson at the sampled sites. In addition to characterizing changes in the local paleoenvironment, we propose a sequence stratigraphic model for the section based on inferred local sea-level fluctuations. We leverage this sequence stratigraphic framework to correlate the Florida Shell section with other studied sections in the Charlotte Harbor area. The development of this new site provides a workable basis for more detailed studies of the long-term paleoecological and paleoenvironmental evolution of southwestern Florida. 

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4. CONFLICTING BODY-SIZE TRENDS ACROSS THE PLIO–PLEISTOCENE MOLLUSCAN TURNOVER EVENT IN THE WESTERN ATLANTIC DESPITE SUBSEQUENT NUTRIENT LIMITATION

   https://doi.org/10.1130/abs/2023AM-391080  

   Anderson, Brendan; Behn, Jessica R.; Betz, Amy; Petsios, Elizabeth; Allmon, Warren D.; Lieberman, Bruce; Hendricks, Jonathan (August 2023, Geological Society of America Abstracts with Programs)

   Preliminary data indicate between the latest Pliocene and recent approximately 85% of bivalves and 90% of gastropod species in Florida and the Atlantic Coastal Plain became extinct, with high levels of origination resulting in similar total species richness in the region today. We expected this event may have impacted molluscan body size as body size in mollusks is generally correlated with nutrient availability and primary productivity, which decreased following the Pliocene closure of the Central American Seaway. Previous work indicated small body size is associated with extinction survival during this event in both bivalves and gastropods. Where all extant and Pliocene members of surviving bivalve clades have been compared, these have also declined in size; comparable studies of all extant and Pliocene members of gastropod clades have not yet, however, been undertaken. We investigated 3 families of gastropods of differing ecology with both high turnover and at least one boundary-crossing lineage in order to assess the impact of the turnover event on each clade’s body size. These were the predatory Conidae, the herbivorous Tegulidae, and the suspension-feeding Turritellidae. These had approximately 65%, 75%, and 90% extinction, respectively, with modern­ diversity at 110%, 100%, and 10% of their respective Pliocene species richness in the region. Despite high levels of turnover, we found no general pattern of body-size change associated with the event either within clades or among boundary-crossing lineages. While many of the largest species of Conidae and Turritellidae did become extinct, this was balanced by the loss of smaller-bodied species, while the Tegulidae increased in size. Among ancestor-descendant pairs, 1 turritellid decreased in size while 1 remained unchanged, 4 Conidae decreased in size while 2 increased in size, and 1 tegulid increased in size. These data suggest that for gastropods there were complex interactions between ecology, extinction, origination, and body-size evolution associated with this event and that a more phylogenetically-diverse dataset is needed to determine whether generalizable patterns exist which may be used to predict responses to future environmental change. 

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5. The rises and falls of turritellid gastropods during the Cenozoic in the western Atlantic

   Allmon, WD; Anderson, BM (July 2024, Museum of Paleontology, The University of Michigan; Papers on Paleontology)

   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 

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