7 Undergraduate Research, Part I (Posters)

Session showcases undergraduate research. Topics include geoscience-related fields (e.g., resources, hydrology, oceanography, climate, environmental science, geospatial, informatics, health, policy, & education). Undergraduate student/s must be the lead author/s presenters with faculty mentor/s as co-author/s. This session welcomes both poster and oral presentation submissions.

Monday, 9 March 2026
9:00 AM - 5:00 PM
RCC, Lower Level Hall

Middle Miocene–Early Pliocene Sharks (Chondrichthyes: Elasmobranchii) from the Peace River, Polk, Hardee and DeSoto counties, Florida, USA

Paper number: 7-8
Program: Technical Sessions
Time: 9:00 AM – 9:00 AM

Authors

Abstract

An abundance of vertebrate fossil remains occurs throughout at least 70 km of the Peace River in Polk, Hardee, and DeSoto Counties, Florida, USA. These fossil remains derive from the Middle Miocene–Lower Pliocene Peace River Formation exposed along and at the base of the Peace River that is represented by phosphatic gravels, sands, and clays. These phosphatic sediments formed as a result of reworking from climatically driven sea level fluctuations during the Miocene and Pliocene, and they have subsequently been subjected to extensive erosion by post-Pliocene fluvial activity that continues today. This situation has enriched river sediments with bioclasts and specifically elasmobranch remains (primarily isolated teeth of sharks) comprising at least 29 species in the following taxa: Notorynchus, Squatina, Ginglymostoma, Carcharias, Otodus, Carcharodon, Alopias, Mustelus, Galeorhinus, Hemipristis, Galeocerdo, Physogaleus, Rhizoprionodon, Negaprion, Carcharhinus, Sphyrna. This represents one of the most diverse fossil elasmobranch assemblages reported from the state of Florida and is also one of the most diverse assemblages in the late Cenozoic elasmobranch fossil record in the USA. Comparison of the Peace River elasmobranchs with those from other submerged and land-based exposures in Florida and elsewhere along the Atlantic and Gulf Coastal Plains of the USA reinforces the biostratigraphic implications of well-known and globally occurring taxa, including the megatooth shark, Otodus megalodon, as related to habitat shifts across central Florida since the Miocene. Moreover, the Peace River elasmobranch assemblage indicates that the Peace River Formation becomes geologically younger to the south and provides a unique means to assess bathymetric variability and the extent of reworking during the deposition of the formation across the study region.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411707

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