PhD Research Project: NERC CENTA - Dispersal patterns in primitive vertebrates

Palaeobiological studies demonstrate that marine invertebrate groups tend to originate in nearshore environments, followed by range expansions into deeper facies dominated by geologically older faunal elements (codified by Jablonski et al. 1983). This onshore-offshore dynamic is thought to be responsible for structuring a major pattern in marine invertebrate communities throughout the Phanerozoic: shallow environments appear to be the locus of major evolutionary innovation, whereas deeper marine ecosystems appear to be refugia. The wider applicability of this pattern, beyond the benthic invertebrate groups upon which the model was erected, is currently being tackled through study of the vertebrate record, where organismal bodyplan also appears to have a substantial influence on palaeogeographic dispersal. One group that has not yet been studied is the conodonts. Conodonts are an enigmatic but wide-ranging and stratigraphically long-lived (Late Cambrian – end Triassic) group. They have an excellent fossil record. Some conodonts exhibit nekto-benthic habits whilst others are considered pelagic, but these interpretations are as yet poorly constrained and analyses of temporal patterns have lacked a phylogenetic framework within which to test macroevolutionary trends. In addition to their prominent use as biostratigraphic tools, at certain intervals conodonts are used to define palaeogeographic provinces (e.g. the Laurentian warm and cold water faunas of the Late Ordovician; multiple realms in the Triassic of Tethys). However, on a macroscale, the clade as a whole quickly becomes cosmopolitan after its first appearance.

By adopting a database approach, this project will seek to use the excellent fossil record of conodonts to test and codify macroevolutionary patterns within palaeoecological and phylogenetic contexts, and will constrain palaeoecological models for taxonomic groupings within conodonts.

This project will focus on the compilation of a database documenting the palaeoenvironmental occurrences of ‘complex’ conodonts (building upon existing data in the Paleobiology Database, http://www.paleobiodb.org, but augmented by substantial data-mining from primary literature), with each occurrence assigned to stratigraphic, palaeogeographic and benthic assemblage zone/intertidal-subtidal-shelf-basin bins (the latter giving an estimate of relative water depth).

Once compiled, the database will be interogated with a focus on testing for phylogenetic, stratigraphic and depositional environment congruence using a variety of cutting-edge statistical methods that have already been successfully used to reconstruct ancestral states within middle Palaeozoic fish as part of a parallel study (Sansom unpublished data). The project will also examine the geographic range of clades over their evolutionary histories, using three different estimates of range size: (i) the number of terranes inhabited; (ii) mean interlocality distance, as assessed using palaeontological GIS; and (iii) area defined by convex hull enclosing all localities and occupancy within these cells. The significance of results will be assessed by comparing empirical ranges for individual family-level clades in each temporal interval against nulls, and also cross-referenced against depositional environmental congruence conclusions. Additionally, a number of phylogenetic hypotheses will be tested and refined, particularly dissecting some of the stratigraphically longer ranging taxa down to species level.

Funding Notes

In addition to completing an online application form, you will also need to complete and submit the CENTA studentship application form available from www.centa.org.uk.

CENTA studentships are for 3.5 years and are funded by the Natural Environment Research Council (NERC). In addition to the full payment of their tuition fees, successful candidates will receive the following financial support.

Annual stipend, set at £14,296 for 2016/17
Research training support grant (RTSG) of £8,000

CENTA students are required to undertake from 45 days training throughout their PhD including a 10 day placement.

References

Donoghue et al 2008 The interrelationships of complex conodonts (Vertebrata). Journal of Systematic Palaeontology 6, 119–153
Jablonski et al 1983. Onshore-offshore patterns in the evolution of Phanerozoic shelf communities. Science, 222, 1123-1125
Sallan et al 2015. The Silurian nekton revolution: Paleozoic jawless fishes exhibited modern form-dependent modes of habitat use. Geological Society of America Abstracts with Programs. Vol. 47, No. 7, p.632
Smith et al 2002. The spatial and temporal diversification of Early Palaeozoic vertebrates. Geological Society, London, Special Publications, 194, 69-83