A new ornithomimosaur from the Lower Cretaceous Trinity Group of Arkansas

ABSTRACT

Whereas ornithomimosaurs (ostrich-mimic dinosaurs) are well known from Asia during the Early Cretaceous, they are less well known from this time in North America. Represented by a single specimen consisting of pedal elements, a new North American taxon, Arkansaurus fridayi, gen. et sp. nov., consists of a nearly complete right foot, recovered from the Lower Cretaceous (Albian–Aptian) Trinity Group of Arkansas. Arkansaurus fridayi can be distinguished from other ornithomimosaurs based on differentiated pedal unguals, a laterally compressed third metatarsal that is ovoid in proximal view, and a distal ungual with a very weak flexor tubercle, lacking spurs. The condition of this third metatarsal suggests that Arkansaurus fridayi is more basal than Asiatic ornithomimosaurs of similar age, but consistent with older North American forms. This specimen provides knowledge of a poorly understood radiation of ornithomimosaurs in Appalachia and is the only known saurischian dinosaurian fossil from the state of Arkansas.

http://zoobank.org:pub:EB6910D3-A66D-43FE-A2F6-3BFF4A7B347C

Citation for this article: Hunt, R. K., and J. H. Quinn. 2018. A new ornithomimosaur from the Lower Cretaceous Trinity Group of Arkansas. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1421209.

ACKNOWLEDGMENTS

Reviews and comments by J. Kirkland, M. Loewen, and editor A. Turner greatly improved the manuscript and are appreciated. Comments and productive discussion were provided early in the writing process by A. Farke, M. Wedel, and J. Foster. Early guidance for this project was provided by J. Kirkland, L. Carson Davis, P. Guccione, D. Zachry, W. Manger, A. McCartney, and the University of Arkansas Department of Geosciences, 2001–2003; J., R., and H. Foster, K. and R. Hunt, and the BLM Paleo Team for logistical and moral support; H.-D. Sues, C. Riddell O'Connor, P. Makovicky, D. Naish, T. Lipka, N. Matthews, C. Suarez, J. Lively, J. Mallon, M. Hayden, B. Burger, H. Clark, C. Brochu, J. Kirkland, B. Engh, B. Parker, L. Alcalá, S. King, and B. Creisler for research assistance, advice, and access to literature; R. Gaston for research casts; and D. Boyer (Morphosource). Thanks to M. Suter (University of Arkansas Museum); K. Carpenter (Utah State University–Eastern Prehistoric Museum); M. Fox, J. Henderson, and C. Norris (Yale Peabody Museum of Natural History); H.-D. Sues, M. Carrano, K. Behrensmeyer, and M. Brett-Surman (Smithsonian National Museum of Natural History); R. Scheetz (Brigham Young University Museum of Paleontology); and B. Britt (Brigham Young University) for access to comparable specimens. Special thanks to J. B. Friday for donating the specimen to the University of Arkansas, to L. Carson Davis for research assistance and ongoing support, and to C. Oury and Arkansas Representative G. Leding for their work in designating this specimen as the Arkansas state dinosaur. Paleogeographical map in Figure 1 by R. Blakey under license, Figures 2 and 4 by J. B. Pruitt (Idaho Virtualization Laboratory), and Figure 6 by B. Engh (Dontmesswithdinosaurs.com). This research was funded by a grant from the David B. Jones Foundation to R.K.H., with assistance by L. Shenton and D. Toll (Utah Friends of Paleontology).

Handling editor: Alan Turner.