ASGP (2015), vol. 85: 515–525

FIRST REPORT ON DINOSAUR TRACKS FROM THE BURRO CANYON FORMATION, SAN JUAN COUNTY, UTAH, USA – EVIDENCE OF A DIVERSE, HITHERTO UNKNOWN LOWER CRETACEOUS DINOSAUR FAUNA

Jesper MILÀN (1, 2), Luis M. CHIAPPE (3), David B. LOOPE (4), James I. KIRKLAND (5) & Martin G. LOCKLEY (6)

1) GeomuseumFaxe, Østsjællands Museum, Østervej 2, DK-4640 Faxe, Denmark; e-mail: jesperm at oesm.dk
2) Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark
3) The Dinosaur Institute, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA; e-mail: Chiappe at nhm.org
4) Department of Earth & Atmospheric Sciences, University of Nebraska, Lincoln, NE 68588-0340, USA; e-mail: dloope1 at unl.edu
5) Utah Geological Survey, 1594 W. North Temple, Suite 3110, PO Box 146100, Salt Lake City, UT 84114-6100; e-mail: jameskirkland at utah.gov
6) Dinosaur Tracks Museum, University of Colorado Denver, PO Box 173364, Denver, CO 80217, USA; email: martin.lockley at ucdenver.edu

Milàn, J., Chiappe, L. M., Loope, D. B., Kirkland, J. I. & Lockley, M. G., 2015. First report on dinosaur tracks from the Burro Canyon Formation, San Juan County, Utah, USA – evidence of a diverse, hitherto unknown Lower Cretaceous dinosaur fauna. Annales Societatis Geologorum Poloniae, 85: 515–525.

Abstract: The newly discovered White Mesa tracksite in the Burro Canyon Formation represents a snapshot of a diverse, Lower Cretaceous dinosaur fauna from south-eastern Utah. The tracks were found at a construction site where the sandstone had been bulldozed and broken up. All tracks were found as deep, well-preserved natural casts on the underside of the sandstone slabs. Individual theropod tracks are 19–57 cm in length; one peculiar track shows evidence of a possible pathological swelling in the middle of digit III and an apparently didactyl track is tentatively assigned to a dromaeosaurid. Individual sauropod tracks are found with pes lengths of 36–72 cm, and interestingly, three distinct shapes of manus tracks, ranging from wide banana shaped to rounded and hoof-like. Ornithopods are represented with individual tracks 18–37 cm in length; a sin gle track can possibly be attributed to the thyreophoran ichnogenus Deltapodus. Zir con U-Pb dating places the track-bearing layer in the Barremian, contemporary to the lower Yellow Cat Member of the Cedar Mountain Formation, which has a similar faunal composition based on both tracks and body fossils. This new track-fauna demonstrates the existence of a diverse dinosaurian assemblage in the lower part of the Burro Canyon Formation, which hitherto is not known to yield skeletalre mains.

Manuscript received 7 July 2015, accepted 16 September 2015