Terrestrialisation in vertebrates using evidence from synchrotron tomography
Supervisory Team /- Dr Roger Benson, University of Oxford
- Dr Stig Walsh, National Museums of Scotland
Key Words / Palaeobiology, evolution, amniote origins
Overview
Invasion of the land was a major transition in vertebrate evolution. A deep evolutionary divergence over 350 million years ago gave rise to amphibians (salamanders, frogs, caecilians) and amniotes (mammals and reptiles, including birds) (Hedges et al. 2015; Clack et al. 2016). Fossils from this time are rare, but provide critical data on the anatomical transformations involved in terrestrialisation, early ecological diversification, and the timing of radiations that ultimately gave rise to half of all living vertebrate species.
Westlothiana and Casineria are important early fossils that were originally reported as amniotes (Smithson 1989; Paton et al. 1999). Amniotes show significantly greater adaptation to terrestrial life than amphibians (e.g Janis & Keller 2001), and comprise many more species today. However, the specimens that would shed light on amniote origins have been difficult to study because of their delicate preservation in closed slabs of rock.
Drawing of the skeleton of Westlothianain its slab. Only surface details are visible. But much more is present within the rock. From Smithson (1989)
Methodology
The project will use synchrotron tomographic data of both Westlothiana and Casineria. These data provide unprecedentedly well-resolved 3D data on the skeletons of these animals, which will be used to generate 3D anatomical renderings at high resolution. Combined with examination of Carboniferous tetrapod fossils worldwide, the resulting data will be used to revise our knowledge of phylogenetic relationships on the amniote stem lineage and to assess the structure and functional adaptations of the limbs and skulls of these important transitional fossils. This work will advance our knowledge of amniote origins and of terrestrialisation in vertebrates.
Timeline
Year 1: Literature review, training in 3D data visualisation/segmenting, virtual extraction of fossils from rocks using scan data. CT scanning.
Years 2 and 3: Comparative anatomy, description, phylogenetic analysis. Functional interpretations. Synthesis.
Year 4: Data integration, thesis completion, papers for international journals/conference presentation.
Training & Skills
3D data visualisation/segmenting, comparative anatomy, phylogenetics, palaeobiology
References & Further Reading
Clack JA 2012. Gaining Ground. Indiana University Press
Clack JA et al. 2016. Nature Ecology and Evolution 1, 0002
Hedges SB et al. 2015. Molecular Biology and Evolution 32, 835–845
Paton RL et al. 1999. Nature 398, 508–513;
Smithson TR 1989. Nature 314, 676–678;
Smithson TR et al. 1994.Transactions of the Royal Society of Edinburgh 84, 383–412.
Further Information
Dr Roger Benson