PhD: Out from the shadow of the dinosaurs? Dietary diversity and niche partitioning in Cretaceous and Palaeocene mammals

Project Highlights:
Use new techniques to shed fresh light on a long-standing evolutionary question – the diversity of mammals after the extinction of dinosaurs
Acquire a suite of skills for quantitative statistical analysis of textures, morphology and evolutionary patterns
Opportunities to travel to collect data from fossil collections across Europe and the US, and conduct fieldwork in New Mexico

This project will use new techniques to address one of the perennial questions in palaeontology: the impact of dinosaurs and their extinction on mammal evolutionary history. A number of recent studies have focussed on the timing of mammal diversification (e.g. Wilson et al. 2012, Close et al. 2015), but whether mammal diversity was supressed during the ‘reign’ of dinosaurs and released only after their demise is a question of more than just numbers of species – it's a question of ecological diversity. Morphological analysis of well-preserved articulated mammal skeletons of Jurassic age is starting to paint a picture of mammals occupying a broader range of ecological niches than previously thought, but the majority of fossil mammals are known only from disarticulated remains and teeth, and are not amenable to this type of functional analysis. Consequently, the degree to which their ecological diversity was affected by the K-Pg extinction, and the pattern of ecological diversification during the Palaeocene, have been difficult issues to address.

This project will employ a new approach: textural analysis of tooth microwear. The application of this approach to early mammals was recently pioneered by the supervisors (Purnell et al. 2013, Gill et al. 2014). You will combine this with other dietary proxies (isotopic data, mesowear and shape analysis of teeth) in phylogenetic context, to conduct the first multidisciplinary, multiproxy investigation of the dietary diversity of mammals before and after the extinction, and of the subsequent patterns of trophic niche occupation and partitioning. You will establish the dietary guilds to which the early members of modern mammal lineages belong. Textural analysis of microwear has revealed hidden trophic diversity in Jurassic mammals, indicating that lineage splitting during the earliest stages of mammalian evolution was associated with ecomorphological specialization and niche partitioning (Gill et al. 2014). This project, applying the approach to Cretaceous and Palaeocene fossils, will similarly yield new insights into the evolutionary history of mammals.

This project is ideal for applicants with a first degree in geological or biological sciences and an aptitude for quantitative analysis. At Leicester you will join a dynamic group of researchers, PhD and Masters students working on novel analyses of diet and trophic niche in fossil vertebrates.

Methodology
The project will focus on material from the San Juan Basin of New Mexico – one of the world’s premier localities for Palaeocene mammal fossils. The collections, held in the New Mexico Museum of Natural History, include new material recently excavated by the supervisors, and the project offers opportunities for fieldwork in New Mexico. Dietary analysis will employ quantitative 3D texture analysis of microwear using methods developed at Leicester (Purnell et al. 2013, Gill et al. 2014). Combining this with mesowear analysis, isotopic data, functional morphological analysis, and quantitative phylogenetic methods will allow robust analysis and hypothesis testing of the role of feeding and diet at different temporal and spatial scales. This approach will allow independent testing of dietary hypotheses, and evaluation of specific roles within broader dietary guilds, and has the potential to pick up dietary transtions that predate and potentially drive morphological adaptation of teeth to new functional roles.

Further reading
Close RA, Friedman M, Lloyd GT, & Benson RB (2015) Evidence for a Mid-Jurassic Adaptive Radiation in Mammals. Current biology : CB 25(16):2137-2142.
Gill PG, Purnell MA, et al. (2014) Dietary specializations and diversity in feeding ecology of the earliest stem mammals. Nature 512:303-305.
Purnell MA, Crumpton N, Gill PG, Jones G, & Rayfield EJ (2013) Within-guild dietary discrimination from 3-D textural analysis of tooth microwear in insectivorous mammals. J. Zool. 291(4):249-257.
Williamson TE, Brusatte SL, Secord R, & Shelley S (2015) A new taeniolabidoid multituberculate (Mammalia) from the middle Puercan of the Nacimiento Formation, New Mexico, and a revision of taeniolabidoid systematics and phylogeny. Zool. J. Linn. Soc.
Wilson GP, et al. (2012) Adaptive radiation of multituberculate mammals before the extinction of dinosaurs. Nature 483(7390):457-460.