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TITLE: New evidence of large dicynodonts in the upper Moenkopi Formation (Middle Triassic) of northern Arizona
AUTHOR: Sterling J. Nesbitt and Kenneth D. Angielczyk
JOURNAL: PaleoBios
PUBLISHED: Oct 31, 2002
NOTES: 22(2)
ABSTRACT: Large dicynodont tracks and bones have been discovered in the Perovkan age (= Early Anisian) upper Moenkopi Formation of northern Arizona, representing the earliest appearance of this group in North America. Dicynodont fossils are found throughout the stratigraphic section of the Holbrook Member and include a worn tusk, a cervical vertebra, two isolated footprints, and a trackway. The tusk was discovered in the uppermost sandstone of the Holbrook Member, making it the highest known occurrence of a vertebrate in the Moenkopi Formation sequence. The cervical vertebra was discovered in a conglomerate channel midway through the stratigraphic sequence of the Holbrook Member. The trackway was published as the holotype of the ichnospecies Therapsipus cumminsi, and the isolated footprints also can be referred to this taxon. One of the isolated footprints was found at nearly the same stratigraphic level as the vertebra, whereas the other was discovered in the lowermost sandstone of the Holbrook Member and represents the lowest occurrence of dicynodonts in the formation. The Moenkopi dicynodont bones show similarities to the Triassic Kannemeyeriiformes. In particular, the large size ot the tusk and its surface texture compare well to those of other kannemeyeriiforms. The cervical vertebra shows similarities to the Late Triassic Placerias gigas, but lacks a strongly amphicoclous centrum. Kannemeyeriiforms include the largest dicynodonts of the Early and Middle Triassic, and our material supports the presence of this group in the Middle Triassic of North America.
COLLECTION: PaleoBios Archive Public
ID: 149

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    BNHM      University of California, Berkeley