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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 

Lead Supervisor: Daniel Field, Earth Sciences

Co-Supervisors: Alexander Liu, Earth Sciences and Peter Makovicky, Field Museum

Importance of the area of research concerned: 
The end-Cretaceous mass extinction event 66 Ma marks the dawn of the modern world: This extinction event witnessed the loss of ~70% of all species on Earth, and most major groups of tetrapod vertebrates diversified rapidly in its aftermath. However, the selective factors associated with this extinction event that drove patterns of vertebrate extinction and survival in the terrestrial realm are only beginning to be unravelled [e.g. Field et al. 2018]. Toward clarifying these patterns, this project will investigate macroevolutionary patterns in avialan genome size and growth rates across the end-Cretaceous mass extinction event in order to determine whether these parameters influenced patterns of avian survivorship. Today, birds are the most diverse group of living tetrapods, represented by nearly 11,000 living species. Recent work has established that the end-Cretaceous mass extinction played a central role in driving a major burst of adaptive avian diversification in the earliest Cenozoic; however, the biological factors distinguishing the surviving lineages of modern birds vs. lineages of stem avialans that perished are unknown.
Project summary : 
The advent of high-resolution synchrotron microtomography has enabled the non-destructive, repeatable collection of histological data from precious fossils. Although proof-of-concept work has illustrated the value and promise of this approach [e.g. Dumont et al. 2016], such techniques have yet to be applied to one of the most significant questions in contemporary macroevolution: survivorship across the end-Cretaceous mass extinction. This project will draw on cutting-edge analytical tools, such as synchrotron microcomputed tomography in order to non-invasively and non-destructively examine histological correlates of genome size and growth rate and evaluate how these changed across the end-Cretaceous mass extinction.
What will the student do?: 
In this project, the student will perform a series of analyses aimed at quantifying osteocyte lacuna dimensions (correlates of genome size in vertebrates [D’Emic and Benson 2013]), lines of arrested growth to estimate growth rates, and vascular density in a comprehensive suite of avialan fossils spanning the end-Cretaceous mass extinction event. The student will work extensively with high-resolution synchrotron computed tomographic data using a variety of software packages in order to visualise, assess, quantitatively measure, and illustrate patterns of change in these parameters against phylogenetic and stratigraphic frameworks. The student will gain familiarity with a wide range of statistical and comparative phylogenetic analyses in order to interpret the data, as well as stem and crown avian phylogeny and the avialan fossil record. Beyond implications for understanding the end-Cretaceous mass extinction specifically, the analytical approach taken here will be instrumental for assessing similar parameters across other mass extinction horizons, and as a baseline for investigating biological correlates associated with the ongoing biodiversity crisis in the present day.
References: 
Field, D.J., et al. 2018. Early Evolution of Modern Birds Structured by Global Forest Collapse at the End-Cretaceous Mass Extinction. Current Biology, vol. 11, pp.1825-1831.
Dumont, Maïtena, et al. 2016. Synchrotron imaging of dentition provides insights into the biology of Hesperornis and Ichthyornis, the “last” toothed birds. BMC Evolutionary Biology, vol. 16, pp.178.
D’Emic, D.M., & Benson, R.B.J. 2013. Measurement, variation, and scaling of osteocyte lacunae: a case study in birds. Bone, vol. 57, pp.300-310.
Applying
You can find out about applying for this project on the Department of Earth Sciences page.