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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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The rises and falls of turritellid gastropods during the Cenozoic in the western Atlantic
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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- Award ID(s):
- 2225014
- PAR ID:
- 10558878
- Publisher / Repository:
- Museum of Paleontology, The University of Michigan; Papers on Paleontology
- Date Published:
- Issue:
- 39
- ISSN:
- 0148-3838
- Page Range / eLocation ID:
- 102-103
- Format(s):
- Medium: X
- Location:
- Ann Arbor, Michigan
- Sponsoring Org:
- National Science Foundation
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