5.13. Reconstruction of AAS ornithopod using a generalized hadrosauroid skeleton as a model. Recovered fossils discussed in text are shaded gray. Artwork by Tracy Ford.
Because UTA-AASO-2003 is composed primarily of postcranial elements (Fig. 5.13) and Protohadros is based upon crania (Head, 1998), it is currently difficult to verify whether they represent independent taxa, or if the AAS specimen represents the postcranial skeleton of Protohadros. Both the AAS specimen and Protohadros are basal hadrosauroids of comparable grade. Although basal hadrosauroid taxa are widespread throughout the Cretaceous, most taxa do not overlap in time or space (Prieto-Márquez, 2010b). The AAS occurs in the Lewisville Member of the Woodbine Formation, whereas the type locality of Protohadros was reported by Head (1998) as occurring in the overlying, younger Arlington Member. However, the stratigraphic distribution of Protohadros is unknown, and the widespread presence of hadrosauroid material throughout the Lewisville and Arlington Members in the area suggests this material may all belong to the same taxon (i.e., Protohadros), which implies it was a widespread and common component of the Woodbine fauna during the early to middle Cenomanian. More cranial material and additional stratigraphic work are needed before this question can be sufficiently answered.
CONCLUSIONS
The Arlington Archosaur Site represents an important addition to our knowledge of middle Cretaceous terrestrial communities, and includes new remains of a non-hadrosaurid hadrosauroid dinosaur. UTA-AASO-2003 has a complex taphonomic history, that consisted of periods of prolonged aerial exposure and low-energy hydraulic transport, early and late diagenetic distortion, followed by recent, post-fossilization weathering. Bite marks on the femur (UTA-AASO-125) suggest that individuals of this taxon were consumed by resident AAS crocodyliforms (Noto et al., 2012). This new specimen is distinguished by its mosaic combination of basal and derived traits, and will contribute to our understanding of basal hadrosauroid anatomy and evolution. Currently there are insufficient skeletal and stratigraphic data to determine whether UTA-AASO-2003 and UTA-AASO-125 belong to Protohadros, or represents a separate taxon. Because the AAS is an ongoing excavation, any additionally recovered material will further clarify the nature of the AAS specimens as well as the diversity of the Woodbine ornithopod fauna.
ACKNOWLEDGMENTS
We thank the Huffines family and Robert Kimball of HC LOBF for granting land access to conduct work at the Arlington Archosaur Site. P. Kirchhoff and B. Walker, A. Sahlstein and B. Carter all donated the specimens discussed herein. The PaleoMap Project, the Earthwatch Institute, the Arlington Tomorrow Foundation, and the Jurassic Foundation provided research funds; and the Dallas Paleontological Society and the Western Interior Paleontological Society provided scholarships to DJM. We heartily thank Arlington Archosaur Site project volunteers A. Sahlstein, R. Fry, A. Miramontes, D. Sumerfelt, B. Carter, A. Osen, R. Colvin, R. Zack, P. Scoggins, J. Beeck, N. Campbell, C. K. Bingman, N. Van Vranken, and T. Dalbey, along with members of the Dallas Paleontological Society and UTA Dinosaurs class students for their assistance excavating the Dinosaur Quarry at the AAS. We include here a special note of thanks to A. Miramontes for his preparation of the specimens discussed herein; his patience and dedication in the lab made much of this study possible. F. M. Dalla Vecchia and J. Kirkland provided important literature references, comments, and advice. Many thanks go to A. McDonald for viewing images of AAS fossils and offering his insight, and for providing data and literature on Eolambia; K. Poole for discussing iguanodontian cladistics,;and D. Tanke for reviewing AAS fossils and providing comments. T. Ford for provided the excellent paleo-artwork. This work would not have been possible without L. Jacobs and D. Winkler at the Shuler Museum of Paleontology at Southern Methodist University for providing access to the Protohadros type specimen. We would also like to thank the editors and one anonymous reviewer for their detailed critique of the original manuscript. Their efforts significantly improved this work.
LITERATURE CITED
Alexander, N. 1976. Father of Texas Geology, Robert T. Hill. Bicentennial Series in American Studies 4. Southern Methodist University Press, Dallas, Texas, 136 pp.
Beall, A. D. 1964. Fabric and mineralogy of Woodbine Sediments, East Central Texas. Ph.D. dissertation, Stanford University, Stanford, California, 171 pp.
Behrensmeyer, A. K. 1978. Taphonomic and ecologic information from bone weathering. Paleobiology 4:150–162.
Bergquist, H. R. 1949. The Woodbine Formation of Cooke, Grayson and Fanin Counties, Texas. USGS Oil and Gas Inventory. Preliminary Map 98.
Brett-Surman, M. K. 1979. Phylogeny and paleobiogeography of the hadrosaurian dinosaurs. Nature 277:560–562.
Brett-Surman, M. K., and J. R. Wagner. 2007. Discussion of character analysis of the appendicular anatomy in Campanian and Maastrichtian North American hadrosaurids: variation and ontogeny; pp. 135–169 in K. Carpenter (ed.), Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Indiana University Press, Bloomington, Indiana.
Campione, N. E. 2014. Postcranial anatomy of Edmontosaurus regalis (Hadrosauridae) from the Horseshoe Canyon Formation, Alberta, Canada; chapter 13 in D. A. Eberth and D. C. Evans (eds.), Hadrosaurs. Indiana University Press, Bloomington, Indiana.
Carpenter, K., and Y. Wilson. 2008. A new species of Camptosaurus (Ornithopoda: Dinosauria) from the Morrison Formation (Upper Jurassic) of Dinosaur National Monument, Utah and a biomechanical analysis of its forelimbs. Annals of the Carnegie Museum 76:227–263.
Casanovas, M. L., X. P. Suberbiola, J. V. Santafe, and D. B. Weishampel. 1999. First lambeosaurine hadrosaurid from Europe: paleobiological implications. Geological Magazine 136:205–211.
Chapman, R. E., and M. K. Brett-Surman. 1990. Morphometric observations on hadrosaurid dinosaurs; pp. 163–177 in K. Carpenter and P. J. Currie (eds.), Dinosaur Systematics: Approaches and Perspectives. Cambridge University Press, Cambridge, U.K.
Cope, E. D. 1869. Synopsis of the extinct Batrachia, Reptilia and Aves of North America. Transactions of the American Philosophical Society 14:1–252.
Dalla Vecchia, F. M. 2006. Telmatosaurus and the other hadrosaurids of the Cretaceous European Archipelago: an overview. Natura Nascosta 32:1–55.
Dalla Vecchia, F. M. 2009. Tethyshadros insularis, a new hadrosauroid dinosaur (Ornithischia) from the Upper Cretaceous of Italy. Journal of Vertebrate Paleontology 29:1100–1116.
Davies, K. L. 1983. Hadrosaurian dinosaurs of Big Bend National Park, Brewster County, Texas. M.S. thesis, University of Texas at Austin, Austin, Texas, 235 pp.
Dodge, C. F. 1952. Stratigraphy of the Woodbine Formation in the Arlington area, Tarrant Co., Texas. Field and Laboratory 20:66–78.
Dodge, C. F. 1968. Stratigraphic nomenclature of the Woodbine Formation Tarrant County, Texas; pp. 107–125 in C. F. Dodge (ed.), Stratigraphy of the Woodbine Formation, Tarrant County, Texas. Geological Society of America Field Trip Guidebook, South Central Section.
Dodge, C. F. 1969. Stratigraphic nomenclature of the Woodbine Formation Tarrant County, Texas. Texas Journal of Science 21:43–62.
Gilpin, D., T. DiCroce, and K. Carpenter. 2007. A possible new basal hadrosaur from the Lower Cretaceous Cedar Mountain Formation of Eastern Utah; pp. 79–89 in K. Carpenter (ed.), Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Indiana University Press, Bloomington, Indiana.