Phylogeny and function of the basal sauropodomorph antiquus

Michael J. Benton and Emily J. Rayfield

The origin and early evolution of has been debated for decades. Fossils are sparse, and phylogenies sometimes conflict. There are profound macroevolutionary questions concerning the diversification of dinosaurs, the timing, the role of mass extinction events, feeding and locomotory adaptations, and how those early dinosaurs eventually replaced the therapsids as dominant medium-sized to large terrestrial tetrapods.

The basal sauropodomorph dinosaur Thecodontosaurus antiquus was named in 1836, and hundreds of bones were found at that time from quarries in Bristol, and redescribed by Benton et al. (2000). However, since then, many more bones have been extracted from fossiliferous rock from another location, and views on basal dinosaur phylogeny have changed. Late basal sauropodomorphs such as Thecodontosaurus were small (~2 m) and bipedal, yet into the early , more derived sauropodomorphs () began evolving a more quadrupedal stance, enlarged body size (~3-6 m), and elongating and specializing their cervical and dorsal vertebrae. By studying Thecodontosaurus and other basal sauropodomorphs, we can begin to better understand why sauropods dramatically changed their life style and body form, and anatomically how such changes initially occurred.

The student will describe the new materials, and complete the osteology of Thecodontosaurus, and produce a new whole-body reconstruction. There will be a particular focus on the vertebral column (with particular focus on the cervical and dorsal vertebrae), limbs, and pectoral and pelvic girdles. This will lead to a comparative study of other and Early Jurassic sauropodomorphs and a study of body size and posture, and especially how body size increased. Studies will explore the size and strength of leg bones, using engineering approaches and CT scans to explore bone microstructure and growth.

Comparative studies will lead to a revised phylogenetic analysis, taking recent work on basal sauropodomorph phylogeny (e.g. Yates 2003) and updating it, and then comparing more widely with other recently described basal saurischians to resolve questions of the relationships of the basal , and when split into and Theropoda.

The project will provide training in vertebrate palaeontology, the interpretation, description and illustration of bones, phylogenetic methods, comparative biomechanical analysis, and numerical macroevolutionary methods. These are all a perfect training for a future career in vertebrate palaeontology research in a university or museum setting.

M. J. Benton et al. Anatomy and systematics of the prosauropod dinosaur Thecodontosaurus antiquus from the Upper Triassic of southwest England. J. Vert. Paleont., 20, 77-108 (2000). A.M. Yates. A new species of the primitive dinosaur Thecodontosaurus (Saurischia: Sauropodomorpha) and its implications for the systematics of early dinosaurs. J. Syst. Paleont., 1, 1-42 (2003). M.J. Benton, J. Forth, & Langer, M.C. Models for the rise of the dinosaurs. Curr. Biol., 24, R87-R95 (2014). D.J. Button, E.J. Rayfield & P.M. Barrett. Cranial biomechanics underpins high sauropod diversity in resource-poor environments. Proc. R. Soc. B, 281, 20142114 (2014).

Training

The student will be trained in scientific writing, anatomical illustration (drawing, photography, digital illustration), systematics, phylogenetic analysis (using state-of-the -art software Paup, TNT, Mr Bayes), CT scanning and digital reconstruction (using our new XMT digital scanner, and Avizo software), bioengineering analysis (using software Blender, Hypermesh), and the full suite of macroevolutionary analytical tools available in R (e.g. geiger, motmot, caper, ape, paleotree, claddis). These tools equip the student perfectly for a broad range of research posts in universities and museums, and are ahead of the curve in most other institutions throughout the UK, Europe, and North America. Additional work placements are planned in major national museums in London, Germany (Stuttgart, Frankfurt, Tübingen), and South Africa (Cape Town, Johannesburg). These will offer opportunities for the student to meet and collaborate with leading researchers and museum professionals worldwide, and help to position the student to apply for postdoctoral positions.

The project can be done within budget. If there are additional costs, it would be for a museum visit to South Africa or China, and we would secure funds from one of the professional societies, as we often do, such as Geological Society, Palaeontological Association, or Society of Vertebrate .