108-7 A Diverse Fish Otolith Assemblage from the Early Paleocene Wills Point Formation of Texas (USA) Documents a Diversifying Post-Extinction Bony Fish Fauna

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

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Abstract:

The early Paleocene marine vertebrate fauna of the Wills Point Formation (Midway Group) is virtually unknown. Its stratigraphic position (between ~62 and 64 Ma) places it within the so-called Patterson Gap. That gap in detailed knowledge on the fossil record of bony fish (Osteichthyes) encompassing the latest Cretaceous and Paleocene obscures our understanding of the dynamics across the Cretaceous mass extinction and the post-extinction recovery and diversification of bony fish at the start of the Cenozoic.

The Wills Point Formation bony fish assemblage preserves vertebrae, fin spines, and parts of skull associated bones. However, it is the growing otolith assemblage with more than 100 specimens from horizons near the top and bottom of the formation that provides the greatest insight into early Paleocene fish diversity. The otolith assemblage includes members of Anguilliformes, Perciformes, and Pempheriformes/Acropomatiformes. Importantly, many of the otolith taxa appear to be representatives of the Percomorpha. Fossils attributable to Acropomatidae (lanternbellies), Serranidae (cf. Serranus? caribbaeus), Ophichthidae (snake eels), and possibly Sphyraenidae (barracudas) all document early records of this clade that radiated after the K-T Extinction to become the largest extant clade of bony fish. The more limited shark tooth assemblage includes a species of Galeorhinus (Triakidae) and fragments of at least one other clade (likely a lamniform or carcharhiniform).

Some of the otolith taxa are shared with the slightly older Clayton Formation in neighboring Arkansas, but the majority of otolith morphologies are new records for the region, showing a greater diversity of clades in the early Paleocene of the Gulf Coast. Overall, the sizes of the otoliths are quite small, reflecting a small body size among species in the fish fauna. In addition, some of the otoliths from the upper part of the formation appear etched and perhaps passed through the digestive system of a predator. The modern ecological parameters of the corresponding fossil taxa suggest not only an ecologically diverse assemblage of benthic and swimming taxa, but also that the Wills Point Formation accumulations do not have a clear bias for a particular lifestyle or taxon. Thus, this diverse fish fauna might be broadly representative of this part of the western Gulf Coast in the early Paleocene.

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

doi: 10.1130/abs/2025AM-8819

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