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GEOREF RECORD

The Late Jurassic Cleveland-Lloyd Dinosaur Quarry as a drought-induced assemblage

Terry A. Gates
The Late Jurassic Cleveland-Lloyd Dinosaur Quarry as a drought-induced assemblage
Palaios (August 2005) 20 (4): 363-375

Abstract

A comprehensive taphonomic analysis has yielded a novel interpretation for one of the most famous dinosaur quarries in the world. The Cleveland-Lloyd Dinosaur Quarry (CLDQ) traditionally has been interpreted as an attritional predator trap. This scenario is based largely on a remarkable 3:1 predator:prey ratio, dominated by the remains of the theropod Allosaurus fragilis. This study addresses the taphonomy of CLDQ by combining analyses of fossils and entombing sediments along with putative modern analogues. Thousands of bones have been excavated from CLDQ, representing at least 70 individual dinosaurs from a minimum of nine genera. The fossils occur in a 1-m-thick fine-grained calcareous mudstone interpreted as a floodplain ephemeral-pond deposit. The bones show minimal carnivore modification and surface weathering, whereas approximately 1/3 of the elements studied possess pre-depositional fractures and evidence of abrasion. The vast majority of elements are found horizontal to subhorizontal, without a preferred long-axis orientation. The demographic profile of the CLDQ dinosaur assemblage appears to be highly skewed toward subadult individuals. Numerous lines of evidence question the traditional predator-trap hypothesis. Of the alternatives, catastrophic drought appears to be most consistent with available data. Evidence includes a large assemblage of animals in a low-energy ephemeral-pond depositional setting and geologic and biologic evidence of desiccation. Additional support comes from modern drought analogues that frequently result in mass-death assemblages of large vertebrates. Climatic interpretations during Late Jurassic times are consistent with a semiarid environment characterized by periodic drought conditions.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 20
Serial Issue: 4
Title: The Late Jurassic Cleveland-Lloyd Dinosaur Quarry as a drought-induced assemblage
Author(s): Gates, Terry A.
Affiliation: University of Utah, Department of Geology and Geophysics, Salt Lake City, UT, United States
Pages: 363-375
Published: 200508
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 106
Accession Number: 2005-055744
Categories: Vertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch map
N38°30'00" - N39°45'00", W111°19'60" - W110°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200519
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