28 D13. Recent Advances in Paleoecology/Taphonomy (Posters)

Sunday, 22 September 2024
8:00 AM - 5:30 PM
Hall D

TERRESTRIAL, FRESHWATER, AND MARINE TETRAPODS AND TAPHONOMY IN THE “MESAVERDE” FORMATION (LATE CRETACEOUS, CAMPANIAN), BIGHORN BASIN, WYOMING, USA

Paper number: 28-14
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

The “Mesaverde” Formation, exposed in the Wind River and Bighorn basins of Wyoming, represents an important intermediate location between northern and southern Campanian-aged vertebrate assemblages of Laramidia. The eastern Bighorn Basin, represented primarily by the “Case localities” of Washakie County, has been described previously as an estuarine assemblage including marine, freshwater, and terrestrial taxa. Recent fieldwork by the Raymond M. Alf Museum of Paleontology has resampled these sites and also identified new localities in the inland environments of the western Bighorn Basin in Park County. Research goals include documenting faunal composition as well as taphonomic parameters for vertebrate microfossils.

Washakie County localities include plesiosaurs, mosasaurs, and hesperornithiform birds, consistent with a marine environment along the Western Interior Seaway. Both Washakie and Park county localities include non-avian dinosaurs and crocodylomorphs. Non-avian theropods include Tyrannosauridae, Dromaeosauridae, and Richardoestia gilmorei; troodontids are absent, and similar taxon abundances occur in the coastal Washakie and inland Park county localities. Hadrosaurids dominate in both areas, followed by ceratopsids and rare ankylosaurs. Squamates include Socognathus (Washakie County) and Scincomorpha indet. (Park Co.), both new records for the formation. Among turtles, trionychids are most common in both regions, in addition to adocids; solemydids are abundant at the inland (Park Co.) locations, along with baenids. The giant alligatoroid Deinosuchus and turtle Lophochelys, to date, have been found only in the marine-influenced sites in the eastern Bighorn Basin. Taphonomically, the sites are broadly similar when comparing parameters of average bone particle size and roundness, although one site in the eastern Bighorn Basin shows significantly greater wear on individual fossils.

The presence of Solemydidae is consistent with a minimum age of middle Campanian for the exposures sampled here. The apparent absence of Troodontidae contrasts with age-equivalent formations in southern North America (e.g., Wahweap Formation), but is consistent with patterns to the north in Alberta and Montana (Foremost and lower Judith River formations). Testing hypotheses around faunal endemism requires additional sampling.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-402784

© Copyright 2024 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.