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Type: Theses
Title: Skull Evolution in the Australian Dragon Lizards
Author: Gray, Jaimi Ann
Issue Date: 2018
School/Discipline: Biological Sciences
Abstract: Today, lizards of the family Agamidae are widespread across the continent of Australia, where they are commonly referred to as dragon lizards. Since their arrival from Southeast Asia approximately 30 million years ago, they have radiated to occupy every environment that the continent has to offer, and have been particularly successful in the arid habitats as they arose 7-15 million years ago. The monophyly of the Australian agamids is well established, and they are currently regarded as a subfamily, Amphibolurinae, with relatively well understood taxonomy and phylogeny. By contrast, the morphological diversity among the group is yet to be quantitatively and systematically explored. Here, I use quantitative approaches to explore the morphological variation in the skulls of Australia’s agamid lizard radiation. I used a combination of linear measurements, tooth counts, and two-dimensional and three-dimensional geometric morphometrics to characterise and explore patterns of morphological variation in the Australian dragon lizards. The cranial morphology of the 67 Australian agamid species used in this dissertation is more morphologically diverse than all other members of the agamid family combined. This disparity is achieved by modification of growth patterns, size, and dental characters. All Australian dragons tend to have a similar juvenile phenotype but become more disparate in shape as they approach adulthood. Despite their relatively recent invasion of Australia, the amphibolurine lineage of lizards has evolved a wide variety of different skull shapes, and provides examples of divergence and convergence, as well as the evolution of some extreme skull shapes (e.g. Gowidon, Moloch) that are associated with particular ecological life habits. A phylogenetically informed comparison of skull shapes seen in adult amphibolurines reveals that life habit accounts for differences to a greater degree than phylogenetic constraint. The extent to which this is true for other members of the Australian herpetofauna (e.g. snakes, geckos and skinks) is unclear and requires further work, but this thesis provides a foundation to do so. As well as revealing macroevolutionary patterns among the extant species, all chapters of this thesis advance our knowledge of their skull anatomy, enhance the resources available for interpretation of fossil agamid material, and unlock the potential for deep-time studies of palaeoecological changes.
Advisor: Sanders, Kate
Hutchinson, Mark
Jones, Marc
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2018
Keywords: morphology
geometric morphometrics
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
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