A New Troodontid Theropod, Talos Sampsoni Gen. Et Sp. Nov., from the Upper Cretaceous Western Interior Basin of North America
A New Troodontid Theropod, Talos sampsoni gen. et sp. nov., from the Upper Cretaceous Western Interior Basin of North America Lindsay E. Zanno1,2*, David J. Varricchio3, Patrick M. O’Connor4,5, Alan L. Titus6, Michael J. Knell3 1 Field Museum of Natural History, Chicago, Illinois, United States of America, 2 Biological Sciences Department, University of Wisconsin-Parkside, Kenosha, Wisconsin, United States of America, 3 Department of Earth Sciences, Montana State University, Bozeman, Montana, United States of America, 4 Department of Biomedical Sciences, Ohio University College of Osteopathic Medicine, Athens, Ohio, United States of America, 5 Ohio Center for Ecology and Evolutionary Studies, Ohio University, Athens, Ohio, United States of America, 6 Grand Staircase-Escalante National Monument, Bureau of Land Management, Kanab, Utah, United States of America Abstract Background: Troodontids are a predominantly small-bodied group of feathered theropod dinosaurs notable for their close evolutionary relationship with Avialae. Despite a diverse Asian representation with remarkable growth in recent years, the North American record of the clade remains poor, with only one controversial species—Troodon formosus—presently known from substantial skeletal remains. Methodology/Principal Findings: Here we report a gracile new troodontid theropod—Talos sampsoni gen. et sp. nov.— from the Upper Cretaceous Kaiparowits Formation, Utah, USA, representing one of the most complete troodontid skeletons described from North America to date. Histological assessment of the holotype specimen indicates that the adult body size of Talos was notably smaller than that of the contemporary genus Troodon. Phylogenetic analysis recovers Talos as a member of a derived, latest Cretaceous subclade, minimally containing Troodon, Saurornithoides, and Zanabazar.
[Show full text]