Overview

Project Highlights:

  • First comprehensive study of cranial functional morphology in the closest relatives of archosaurs.
  • Use of cutting-edge biomechanical analysis and digital visualisation techniques.
  • New insights into bizarre morphologies and the rise of one of the most important vertebrate clades.

Birds, dinosaurs, crocodilians, and pterosaurs all belong to the clade Archosauria, an extraordinarily diverse group that dominated terrestrial tetrapod faunas worldwide for nearly the entire Mesozoic Era, and is still highly successful today, with birds comprising around a third of extant tetrapod biodiversity. The diversification of archosaurs during the Triassic following the end-Permian mass extinction event fundamentally reshaped ecosystems on land. 

Archosauria is part of a broader group, Archosauromorpha, which also includes a range of Permian and Triassic species more closely related to archosaurs than to lizards and snakes (lepidosaurs). These non-archosaurian archosauromorphs formed a significant component of Triassic ecosystems (>90 species) and were morphologically highly diverse, including highly specialised herbivores, large apex predators, marine predators with extremely elongated necks, and armoured crocodile-like forms.   

The evolutionary success of archosaurs was underpinned by a distinctive body plan. Classic cranial anatomical features of archosaurs, including the antorbital and external mandibular fenestrae, the closed lower temporal bar, and serrated teeth, evolved in a mosaic fashion among archosauromorphs closely related to archosaurs. In addition, a number of early archosauromorphs evolved bizarre cranial adaptations, such as the extreme downturned premaxilla of proterosuchids (Figure).

Understanding the evolution of non-archosaurian archosauromorphs is critical to unravelling the origins of archosaurs during the Triassic, and taxonomic and phylogenetic work coupled with new discoveries have led to significant recent advances. However, rigorous functional morphological studies have not yet been conducted. This PhD project will characterise changes in cranial functional morphology through the evolutionary transition from basal archosauromorph to early archosaur. The functional significance of cranial modifications such as the acquisition of the antorbital fenestra will be tested, as well as the function of the proterosuchid premaxilla and other bizarre cranial adaptations.       

Adult skull of the Early Triassic archosauriform Proterosuchus fergusi, showing the bizarre downturned premaxilla

Methodology

The overarching objective of this proposal is to conduct a comprehensive investigation of the functional changes occurring through the transition from early archosauromorphs to early crown group archosaurs. Computed tomographic (CT) datasets are available from the project supervisors for several key taxa (e.g. Youngina, Prolacerta, Proterosuchus, Euparkeria, Gracilisuchus) and will be added to via additional CT scanning. The cranial osteology of these key taxa will be reconstructed using digital visualisation and modelling techniques. These restorations will serve as the basis for the reconstruction of jaw adductor musculature. Subsequent biomechanical analyses will include finite element modelling of the skull to test functional performance.  

Training and Skills

The student will benefit from 45 days training throughout their PhD including a 10-day placement. Initially, students will be trained as a single cohort on research methods and core skills. Further project-specific training will include introduction to digitisation methods (e.g. CT-scanning), digital visualisation and processing of 3D data, and statistical programming in R. The student will also receive training in biomechanical modelling techniques and functional morphology.

Timeline

Year 1: Familiarization with literature, existing datasets and digital visualization and modelling techniques (CT-scanning). Acquisition of additional CT datasets. Digital restoration of fossil specimens. Conferences: SVPCA (UK), EAVP (Europe).

Year 2: Continued digital restoration of specimens and reconstruction of soft-tissues. Biomechanical analysis. Conferences: SVPCA (UK), EAVP (Europe).

Year 3: Continued biomechanical analysis and synthesis of results. Write up and submision of thesis. Conferences: SVPCA (UK), SVP (USA).

Partners and collaboration (including CASE)

Dr Butler has published widely on the anatomy and systematics of early archosauromorph reptiles and early archosaurs. He has extensive experience in the application of quantitative approaches to analysis of palaeontological data. Dr Lautenschlager has pioneered the use of digital methods to restore fossil morphology and to reconstruct soft-tissue anatomy. He has comprehensive expertise in the application of biomechanical analysis techniques (FEA) in fossil vertebrates. Dr Bhullar is an expert in the comparative and functional anatomy of extant and fossil reptiles and birds. His group has pioneered several techniques for visualizing soft tissues in adult and embryonic vertebrates, and has extensive experience in digital dissection of fossil data. Dr Ezcurra is a leading expert on the phylogeny, anatomy and macroevolution of Permian and Triassic archosauromorphs. 

Further Details

Ideally, applicants should have a first degree in the geological or biological sciences and an aptitude for computational analysis. Experience in digital methods (CT data analysis, FEA) is desirable.