New fossils from Tanzania reveal the rapid diversification of Archosauria.
Christian A. Sidor (PI) Sterling J. Nesbitt (Senior Personnel)
This grant supports a two-year postdoctoral research associate position for Sterling J. Nesbitt at the University of Washington, under the supervision of Christian A. Sidor (PI). Sidor and Nesbitts recent fieldwork in southern Tanzania has yielded a large collection of archosaur fossils from the Middle Triassic (approximately 240 million years ago). Living archosaurs include birds and crocodiles, but extinct members of this group encompass numerous taxa like aetosaurs, erpetosuchids, and notably, dinosaurs and their close relatives. Utilizing the new collection of fossils, Sidor and Nesbitt will collaborate to describe several species and interpret each in terms of its position on the archosaur family tree. More specifically, they will reanalyze Parringtonia (which was initially named in 1939), provide a complete anatomical description of the dinosauriform Asilisaurus (which they announced in 2010), and describe a new, aetosaur-like taxon and a new rauisuchian. Sidor and Nesbitt will also examine the Tanzanian archosaur fauna as a whole, by revising the biostratigraphy of the archosaur-bearing strata, and by gauging how the group diversified after the Permian-Triassic mass extinction in the Ruhuhu Basin of Tanzania relative to other contemporaneous geologic basins. Vertebrate paleontology fascinates the public. As part of the broader impact goals of this project, Sidor and Nesbit will develop a temporary display at the University of Washingtons Burke Museum, to highlight some of the best specimens from Tanzania and to explain how fossils and rocks can inform scientists about past climates (e.g., the Triassic hot-house world lacked polar glaciers). Sidor and Nesbitt will also curate the collection of archosaur fossils in anticipation of its repatriation to the National Museum of Tanzania in Dar es Salaam. However, research-quality casts will be created and retained at the Burke Museum.
This grant supported a two-year postdoctoral research associate position for Sterling J. Nesbitt (Senior Personnel) at the University of Washington (UW), under the supervision of Christian A. Sidor (PI). Recent fieldwork in the Middle Triassic Manda beds of southern Tanzania has yielded a large collection of fossil archosaurs (the group that includes modern birds and crocodiles), including several new species that represent the earliest members of lineages that dominated much of the Mesozoic Era. This grant supported research that led to the publication of 10 papers, including the descriptions of two of the oldest near-dinosaurs (Nyasasaurus and Lutungutali) as well as a comprehensive family tree of early archosaurs. We also quantified changes in the geographic distribution of tetrapods in the early Middle Triassic (~242 million years ago), which led us to conclude that the end-Permian mass extinction had a profound effect on the animal communities living in the southern part of the Pangean supercontinent. Ultimately, the radiation of archosaurs, including dinosaurs, was probably more closely tied to the recovery from the end-Permian mass extinction than previously realized. The grant supported a variety of broader impact goals. Sidor and Nesbitt have mentored several graduate and undergraduate students at the UW. In addition, some of the Tanzanian fossils were featured in a temporary display at the UW Burke Museum from October 2012 – April 2013 (see attached image). Replicas of the most important fossils will be retained by the Burke Museum, where they will be available for researchers and incorporated into paleontology and evolutionary biology courses as appropriate. However, all of the original fossil material will be returned to the National Museum of Tanzania in Dar es Salaam when this project is completed. These fossils represents a resource that will engender future research opportunities and increased international collaboration, as well as providing a vehicle for educating Tanzanian citizens about this important part of their national heritage.
