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Title: Functional morphology of stereospondyl amphibian skulls
Author: Penrice, Samantha
ISNI:       0000 0004 8501 5104
Awarding Body: University of Lincoln
Current Institution: University of Lincoln
Date of Award: 2018
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Stereospondyls were the most diverse clade of early tetrapods, spanning 190 million years, with over 250 species belonging to eight taxonomic groups. They had a range of morphotypes and have been found on every continent. Stereospondyl phylogeny is widely contested and repeatedly examined but despite these studies, we are still left with the question, why were they so successful and why did they die out? A group-wide analysis of functional morphology, informing us about their palaeobiology, was lacking for this group and was carried out in order to address the questions of their success and demise. Based on an original photograph collection, size independent skull morphometrics were used, in conjunction with analyses of the fossil record and comparative anatomy, to provide a synthesis of the functional morphology of stereospondyl amphibians. Stereospondyls originated in the Carboniferous and most taxonomic groups were extinct at the end of the Triassic. The early Triassic had exceptionally high numbers of shortlived genera, in habitats that were mostly arid but apparently experienced occasional monsoon rains. Genera turnover slowed and diversity was stable in the Middle Triassic, then declined with a series of extinctions of the Late Triassic. Stereospondyls showed the pattern of 'disaster' taxa: rapidly diversifying following a mass extinction, spreading to a global distribution, although this high diversity was relatively short-lived. Geometric morphometrics on characteristics of the skull and palate was carried out to assess general skull morphology and identified the orbital position and skull outline to be the largest sources of skull variation. Comparing anatomy of stereospondyls with extant species revealed that the differences in head shape and orbit positions between stereospondyls allows inference of a range of feeding behaviours, ranging from rapid head swipes, to crushing invertebrates with wide palatal bones, and crocodilian-type ambushing. The range of feeding modalities meant stereospondyl species were able to coexist with minimal competition. The success was, however, short lived, as highly specialised shapes in the middle and Late Triassic probably meant that stereospondyls were not able to adapt to a more generalised lifestyle when the end Triassic extinction eliminated ecosystems.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available