PhD: Tackling taxonomic and taphonomic biases in the Triassic fossil fish record

Ray-finned fishes account for over half of living vertebrates and have a nearly half-a-billion year evolutionary history, surviving and flourishing in the wake of several mass extinctions

Despite thousands of exceptionally preserved fossils, the impact of the Permo-Triassic Mass Extinction on ray-finned fish evolution is particularly poorly constrained

This project will tackle the taxonomic and taphonomic biases that obscure patterns of extinction and recovery, leading to a revised hypothesis of the impact of the Permo-Triassic Mass Extinction on the largest living vertebrate clade.
Ray-finned fishes (actinopterygians) are the most diverse and successful group of vertebrates today, accounting for over half of living vertebrate species. In their nearly half-a-billion-year history they have survived countless mass extinctions, but, in contrast to many other groups, there is limited understanding of the effect of these devastating mass extinction events on their evolution. Despite thousands of exceptionally preserved two- and three-dimensional fossils from early Triassic deposits worldwide, there is a particularly poor understanding of how the Permo-Triassic Mass Extinction (252 million years ago) impacted ray-finned fishes. The reasons for this are two-fold: no robust hypothesis of the taxonomy and relationships of early Triassic ray-fins, and limited comprehension of the taphonomic processes that may have biased the Early Triassic fossil fish record. This project will combine CT scanning, phylogenetic analyses and taphonomic investigations to tackle these biases.

Recent work has established a backbone of relationships amongst early actinopterygians, and the student will use a combination of traditional descriptive methods and CT scanning to place key early Triassic taxa into this phylogenetic framework and answer taxonomic questions. Much of our understanding of fish taphonomy and decay is based on teleost fishes, which display a very different morphology from early actinopterygians, in particular with regard to scale histology. Different types of squamation may have a profound impact on the preservation potential of different fish groups, potentially biasing the fossil record in this key period of earth’s history and skewing our understanding of ray-finned fish recovery after the Permo-Triassic mass extinction. The student will investigate the effects of this through targeted interrogation of scale-bearing and scaleless taxa as well as taphonomic investigation of extant scale-bearing actinopterygians. This research will provide new insights into taphonomic processes acting on ray-finned fishes and the varying preservation potential of different fossil fish groups. It will also contribute to a revised hypothesis of actinopterygian relationships, answering fundamental questions concerning the impact of the Permo-Triassic mass extinction on the evolution of the largest living vertebrate clade.

Methodology:
This project will focus on taxonomic and taphonomic investigations of early Triassic ray-finned fishes. Fish taxa from this time period are represented by dozens of genera and thousands of fossils, ranging from fully articulated three-dimensional specimens to disarticulated two-dimensional scale remains. The student will use a combination of traditional descriptive and CT scanning techniques to describe key specimens from this time period, revising the taxonomy of pivotal taxa and investigating their relationship to living actinopterygian groups. This will involve visiting museums around Europe and worldwide where feasible. This work will be complimented by taphonomic investigations focussing on collecting morphological data to explore potential preservational biases impacting the Triassic fish fossil record. There is potential for an experimental component investigating the impact of different scale morphologies and histologies on fish decay, disarticulation and preservation potential of key early Triassic groups.

Training and Skills:
The student will be trained in CT scanning and segmentation, comparative anatomy and description, taxonomic and phylogenetic analyses, statistical methods, and taphonomic experimental design. The student will also receive training in how to write and illustrate scientific papers, apply for grants and prizes, present work at conferences and scientific meetings, and network with peers and other scientists. There may also be opportunities for undergraduate teaching and research supervision. These form the basis of an outstanding skill set, combining traditional and state- of-the-art techniques, that will facilitate a successful research career for the student.

Timeline:
- Year 1: Literature review, museum visits, comparative anatomy data collection, taphonomic experimental design.
- Year 2: Museum visits, experimental taphonomy set up and implementation, phylogenetic analysis, taphonomic character matrix development.
- Year 3: Synthesis, completing thesis, writing manuscripts (although manuscripts will be written throughout project).

Partners and collaboration (including CASE):
This project will be carried out in collaboration with the Natural History Museum, London. Dr Zerina Johanson will provide additional supervision. The collections at the NHM represent a world-leading resource, with exceptionally preserved material that is of key importance to this project. Dr Johanson has extensive experience of CT scanning and anatomical interpretation and will assist the student in these areas.

Further Details:
Dr Sam Giles, University of Birmingham (s.giles.1@bham.ac.uk). We particularly encourage applications from backgrounds under-represented in Earth Science subjects.