New archosauromorph fragments from the Dockum Group of Texas and assessment of the earliest dinosaurs in North America

Abstract

Three small and gracile jaw fragments are recovered from the Boren Quarry, one of the lowest fossil quarries of the Upper Triassic Dockum Group of Texas. The specimens are referred to archosauromorphs, where the morphology of the dentary and teeth of two specimens resemble what is observed in basal saurischians. Growing numbers of early dinosaur fossils from the lowest quarries of the Dockum Group of Texas which correspond to the lowermost Norian raises doubts concerning early dinosaur dispersal during the late Carnian-early Norian interval and the first occurrence of North American dinosaurs which might have happened earlier than previously suggested.

Keywords:

• Upper Triassic
• Dockum Group
• Archosauromorpha
• Dinosauria
• early dinosaur dispersal

Acknowledgements

The author would like to thank Sankar Chatterjee for providing the material, Doug Cunningham and Kendra Dean Wallace for preparing the specimens, and Bill Mueller for taking photographs of the specimens and sharing his personal data and observations. The author also wishes to thank the staff at the Museum of Texas Tech University for their friendly attitude.