Overview

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.

Conodont bedding plane assemblage with conodont elements preserved in a natural association (lower left) and traces of the eye cartilage (upper right).

Methodology

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, 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.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Project-specific training will include: conodont anatomy, phylogeny and diversity (Sansom, Purnell); palaeontological databasing, including the Paleobiology Database (Butler); quantitative macroevolutionary and biogeographical analysis (Butler, Sallan).

Timeline

Year 1: Data gathering, including determining the taxonomic range of conodonts to be studied and to identify suitable primary sources for the project.  Training in the utility of the PaleoDB (data entry, exploration and data extraction).

Year 2: Commence data analyses, establish robust qualitative and quantitative methods where appropriate. Refining published phylogenies. Integration of palaeoenvironmental/palaeogeographic distribution database and palaeogeographic maps (using GIS). Presentation of initial results at Palaeontological Association Annual Meeting

Year 3: Data analysis including biogeography methods, correcting for sampling bias and testing. Presentation of project results at Geological Society of America. Writing the thesis will take place during the final year, but papers will be published throughout the project.

Partners and collaboration (including CASE)

Dr Sansom is an expert in the study of early vertebrates, with particular emphasis on phylogenetic and environmental diversity during the Palaeozoic. Prof Purnell is one of the leading authorities on conodont palaeobiology and phylogeny with particular emphasis on ‘complex’ conodonts. Dr Butler has extensive experience with palaeontological databases, particularly the Paleobiology Database, as well as quantitative analysis of fossil data.

Further Details

Dr Ivan Sansom (I.J.Sansom@bham.ac.uk)