Early Jurassic impacts on ray-finned fish diversity and ecosystem function
Exceptionally preserved fossils from this time period offer a unique window into the evolution of teleost fishes and their role and place in ecosystem recovery.
This project will uncover underappreciated taxonomic, morphological and ecological diversity in ray-finned fishes.
The early Jurassic was a period of ecological turmoil, affected both by the aftermath of the end-Triassic Mass Extinction and the Toarcian Oceanic Anoxic Event (TOAE).
Three-dimensional exceptionally preserved fossils from this time (Lagerstätten) provide a unique window into evolutionary innovations and ecosystem recovery. Although reptiles and invertebrates (e.g. ammonites) from this period have been well-described, the associated fishes are largely undocumented, often lumped into poorly defined taxa such as Pachycormus.
This is despite considerable variation between individuals apparently of the same species, undoubtedly masking important ecological variation during this period. Moreover, this lumping means that an accurate account of fish diversity is lacking, and impacts of extinction and anoxic events cannot be fully understood.
Fossil fishes such as those from the Strawberry Bank (Somerset, UK) and Holzmaden (Southwest Germany) faunas provide ample material from the Toarcian to investigate fish diversity in the aftermath of the TOAE.
The Strawberry Bank Lagerstätte occurs at most 1 million years after the event, and possibly concurrent with the TOAE in a recovery phase still affected by high extinction rates (Williams et al. 2015).
CT-scanning of well-preserved specimens will be used to revise taxa such as Caturus, Lepidotus (both holosteans, a group that is today represented only by gars and the bowfin), Leptolepis and Pachycormus (both teleosts, a group that today accounts for over half of living vertebrate diversity) and test existing phylogenetic hypotheses (Lopez-Abarello & Sferco, 2018; Giles et al. 2018).
The large number of specimens, especially from Strawberry Bank, presents an opportunity to look at morphological variation within species and at different ontogenetic stages.
Specimens from both Strawberry Bank and Holzmaden also display soft tissue preservation, including exceptionally preserved structures of the gut, with the potential to reconstruct diet and feeding mode, and ecological role within the broader ecosystem.
This project will focus on descriptive and taxonomic investigations of exceptionally preserved early Jurassic ray-finned fish fossils.
Many hundreds of fossils are known from this time period, spanning tens of genera. Museum collection visits will be made to Bath, Natural History Museum London and the State Museum of Natural History Stuttgart in order to view the fossils and select specimens for CT-scanning and other measurements to capture morphological variation between individuals.
CT-scanning will focus on internal anatomy such as the braincase, inner portions of the jaws, gill skeleton and gut. CT reconstructions will also be used to identify different ontogenetic growth stages, focusing on braincase ossification, vertebral ossification, and any other morphological features showing similar changes (eg. caudal fin).
Descriptions of the anatomy will be used to generate phylogenetic hypotheses of relationships, as well as to identify potential new species.
Training and skills
The student will be trained in CT scanning and segmentation, comparative anatomy and description, taxonomic and phylogenetic analyses, statistical methods.
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.
Partners and collaboration
This project will be carried out in collaboration with the Bath Royal Literary and Scientific Institution and the Natural History Museum, London.
These collections represent world-leading resources, with exceptionally preserved material that is of key importance to this project. The BRLSI has been coordinating international research collaborations into Strawberry Bank for more than a decade and their Collections Manager, Matt Williams, has made the Lagerstätte his palaeontological specialism.
Dr Zerina Johanson (Natural History Museum) is an expert on early vertebrate evolution, currently holds grants and co-supervises two PhD projects with Sam Giles, including on the evolution of teleost fishes.