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Couple More New Papers

Hi Again -

   A few more papers of interest to the group:

Gates, T. A. 2005. The Late Jurassic Cleveland-Lloyd Dinosaur Quarry as a drought-induced assemblage. Palaios 20:363-375.

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.

Colson, M. C., Colson, R. O., and Nellermoe, R. 2004. Stratigraphy and depositional environments of the upper Fox Hills and lower Hell Creek formations at the Concordia Hadrosaur Site in northwestern South Dakota. Rocky Mountain Geology 39:93-111.

ABSTRACT: Many of the dinosaur-bearing bone beds in the Hell Creek Formation of the Dakotas and Montana involve multiple species preserved in the upper Hell Creek Formation. In contrast, the Concordia Hadrosaur Site is monospecific with respect to dinosaurian taxa and is situated in the lower Hell Creek Formation in a lithostratigraphic unit we associate with the Little Beaver Creek Member. This member consists of organic-rich sandstones, siltstones, and claystones that are distinctive within the Hell Creek Formation based on their uniformly fine grain size, purplish color, and presence of highly lignitic shale rather than coal. Similar lignitic deposits occur at other marine-terrestrial boundaries of the Fox Hills-Hell Creek Formations in the Little Missouri and Missouri River valleys.
The bone bed at the Concordia Hadrosaur Site (CHS) is associated with an extensive coastal swamp rather than a localized fluvial subenvironment such as river channel, floodplain, or abandoned channel. The bone bed itself lies at the transition from an extensive swamp (represented by highly organic mudstones) to a more fluvially dominated, distributary environment characterized by variegated mudstones, siltstones, and channel sandstones.
The thirty meters of exposed section at the Concordia site include the top of the Fox Hills Formation and lower parts of the Hell Creek Formation. We identify marine silts, muds, and sands, coastal dune sands, coastal swamp muds and silts, and fluvial sands and silts. The sediments are indicative of the marine-terrestrial transition from upper shoreface and foreshore environments to a complex system of coastal dunes, swamps, and distributary channels that formed during the progradation of the Hell Creek sediments into the Cretaceous Fox Hills seaway. Locally, grain size and organic fraction varied due to differences in the proximity to distributary channels, supply of organic material, and water depth.
Despite the concentration of bones dominated by a single species in the CHS bone bed, the high clay fraction of the bone bed matrix, combined with the fact that the lowest part of the bone bed has the greatest clay fraction, indicates that the bones were not introduced by way of a high-energy, catastrophic event, such as a flood. Rather, the bones accumulated in an area of quiet standing water. Although preliminary examination of the bones is consistent with this depositional interpretation, it does not necessarily provide direct support for it.

Yuan, C., Zhang, H., Li, M., and Ji, X. 2005. Discovery of a Middle Jurassic fossil tadpole from Daohugou region, Ningcheng, Inner Mongolia, China. Acta Geologica Sinica 78:145-148.

Just what it sounds like. Again, this is NOT the English Edition of this journal.

Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
and     dinogami@hotmail.com

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