108-5 A Taxonomically and Ecologically Diverse Marine Vertebrate Assemblage at the end of the Cretaceous in Texas (USA)

Session: The Cretaceous-Paleogene (K-Pg) Boundary Interval: From Large-Scale Geological Events to Mass Extinction Mechanisms (Posters)

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Abstract:

The end Cretaceous mass extinction greatly impacted marine ecosystems globally. However, detailed knowledge of vertebrate faunal diversity just prior to and after the mass extinction lag behind other marine clades, and thus the exact global (and regional) setting of the extinction is not well known. The late Maastrichtian Corsicana Formation exposed in eastern parts of Texas contains significant accumulations of marine vertebrate fossils that have not been examined in detail. In addition, the proximity of Texas to the Chicxulub Impact makes this resource valuable in examining the role that the impact may have had in the immediate geographic region. The uppermost Corsicana Formation fauna includes a minimum of 29 taxa spread across 19 families including sharks, rays, and bony fishes. The shark fauna is the most taxonomically diverse with members of Lamniformes (including white sharks Lamnidae and sand sharks Odontaspididae), Carcharhiniformes (including cat sharks Scyliorhinidae and requiem sharks Carcharhinidae), Hexanchiformes (cow sharks Hexanchidae), Squaliformes (dogfish Squalidae), and Orectolobiformes (carpet sharks Orectolobidae and collared carpet sharks Parascyllidae). The rays and relatives include species of Torpedinidae (electric rays), Dasyatidae (whiptail rays), Ganopristidae (extinct sawskates), Myliobatidae (eagle rays), and Rhinobatidae (guitarfish). Most bony fish skeletal fragments remain unidentified, but identified teeth include Enchodus (Enchodontidae) and Albula (Albulidae). At present, the teeth of Enchodus and Scyliorhinidae are the most common among the identified specimens. This faunal assemblage includes pelagic and benthic taxa that likely derived from both shallow and deeper water environments. Their generalist and specialist ecological roles were diverse with durophagous taxa alongside meso and apex predators. That aspect of habitat and ecological diversity suggests that this fauna represents a broad marine sampling and could provide a good point of comparison for examining faunal dynamics across the mass extinction. In addition, this diverse latest Maastrichtian fauna suggests that the mid-Campanian marine extinction either did not significantly impact this region or that marine vertebrate diversity rebounded prior to the end of the Cretaceous. Overall, this fauna would not support the proposal of a sustained decline in marine vertebrate faunal diversity leading up to the mass extinction. However, the fauna includes a mixture of taxa that did not survive into the Paleocene, taxa with a reduced Cenozoic diversity, and diverse clades living today.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8784

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