Form and function of the teeth and jaws of fossil rhynchocephalians

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Rhynchocephalians were a once globally distributed order of diapsid reptiles that thrived in
the Mesozoic but today are represented by a single taxon. Despite being the sister group to
the largest order of extant reptiles (Pansquamata: lizards, snakes, and relatives) there has
been very scarce quantitative investigation into the dietary ecologies of fossil members of
this order. When reconstructing the dietary palaeoecology for any fossil taxon, it is vital that
we not only understand the limits of what we can infer from living relatives but also what
makes a good modern analogue. Though bearing a superficial resemblance,
rhynchocephalians and pansquamatans diverged over 238 Myr and have accumulated many
anatomical differences, key amongst which is tooth implantation. Here I set out to
investigate whether the diet of fossil rhynchocephalians can be reconstructed based on the
functional morphology of the teeth and jaws of extant lizards, and whether acrodont or
pleurodont lizards are better modern analogues. First, I explored the diversity and
phylogeny of rhynchocephalians based on new fossil material. Second, I investigated trends
in the morphology of the teeth and jaws of lepidosaurs using phylogenetic generalised least
squares. Third, I investigated the effect that diet, phylogeny, and tooth implantation type
had on the shape of lepidosaurian teeth and jaws. Fourth, I explored the functional
morphology of the jaws of rhynchocephalians using a variety of biomechanical analyses. The
results here lead me to conclude that the dietary ecology of extant lizards generally cannot
be inferred directly from gross morphology and therefore we should not rely on shape alone
to infer diet in fossil rhynchocephalians, and that the teeth of acrodont lizards are more like
those of acrodont rhynchocephalians than pleurodont lizards. Future studies should focus
on the teeth of lepidosaurs, using analyses based on surface complexity and microwear.
Date of Award1 Oct 2024
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorMichael J Benton (Supervisor), Emily J Rayfield (Supervisor), David I Whiteside (Supervisor) & Pamela G Gill (Supervisor)

Keywords

  • Rhynchocephalia
  • Lepidosauria
  • Biomechanics
  • Morphology

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