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A tale of two sites: A taphonomic comparison of two Late Triassic (Chinle Group) vertebrate fossil localities from New Mexico

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Andrew B. Heckert Ph.D., Assistant Professor of Geology (Creator)
Institution
Appalachian State University (ASU )
Web Site: http://www.library.appstate.edu/

Abstract: New Mexico Museum of Natural History (NMMNH) localities 3379-3381 are located on the western flank of the Lucero uplift in central New Mexico and are approximately 250 Ma old. The site, which is low in the Bluewater Creek Formation of the lower Chinle Group has produced an astonishing amount of fragmentary remains of Rutiodon-grade phytosaurs, large indeterminate metoposaurids, Apachesaurus sp., and indeterminate reptiles, archosaurs and the lungfish Arganodus. The fossils occur over a large area and are weathering out of fine-grained overbank deposits and in some instances occur in sandbars in shallow channel deposits. None of the fossils are articulated or associated. The bones themselves display stage 3 to stage 4 weathering with splintered ends and longitudinal cracks along the bone shafts, indicating that the animals were subaerially exposed to decay and weathering for a long period of time. Elements recovered include scutes, vertebrae, limb bones, fragmentary skull bones and a large number of phytosaur teeth. In direct contrast to L-3380 is the younger Snyder quarry (NMMNH L-3845), located in north-central New Mexico. The Snyder quarry is in the Petrified Forest Formation of the Chinle (RevueltianNorian age) and is approximately 210 Ma old. Thousands of bones have been excavated from this quarry, including the remains of phytosaurs, aetosaurs and coelophysoid dinosaurs. The bones were deposited in a wide, shallow channel and are in excellent condition with essentially no evidence of either weathering or scavenging. The skeletal elements are associated or rarely articulated. These two localities provide an opportunity to contrast two very different taphonomic settings. The Snyder quarry represents a catastrophic event, most likely a forest fire, whereas NMMNH L-3380 represents an attritional accumulation of corpses on a floodplain.

Additional Information

Publication
Zeigler, K.E., Heckert, A.B., and Lucas, S.G., (2002) A tale of two sites: A taphonomic comparison of two Late Triassic (Chinle Group) vertebrate fossil localities from New Mexico. New Mexico Museum of Natural History and Science Bulletin 21, p. 285-290. (ISSN 1524-4156) Archived in NC DOCKS with permission of the editor. The version of record is available at: http://econtent.unm.edu/
Language: English
Date: 2002