Marsupial evolution and morphological diversity is traditionally viewed against the background of marsupial life history, central to which are the highly altricial neonates that actively move towards the teat. It has been suggested that this mode of birth leads to a constraint on the marsupial postcranial diversity. However, apart from phylogenetic investigations, few empirical studies have assessed diversity, patterns of adaptation, or ontogeny of the marsupial postcranium. This thesis contributes to the debate by providing diverse, large-scale empirical data on selected issues of marsupial postcranial evolution, using multidisciplinary approaches with focus on quantitative analysis. Chapter 1 provides an overview on previous research on this topic. Chapter 2 assesses the phylogenetic and functional-anatomical implications of marsupial carpal diversity. Chapter 3 is a phylogenetically informed morphometric analysis of diprotodontian manual digits, demonstrating locomotor adaptations similar to those in placentals and allowing the development of a new locomotor predictor ratio. Chapter 4 shows that functional correlates of digit proportions in Diprotodontia also exist in the placental hystricomorph rodents, which resemble Diprotodontia in ecological diversity. Chapter 5 applies the results from Chapters 2-4 to the mostly extinct diprotodontian suborder Vombatiformes, revealing functionally related parallelism in the hand of vombatiforms and kangaroos and questioning previous concepts of locomotion in early vombatiforms. Chapter 6 focuses on the evolution of marsupial syndactyly using a multidisciplinary approach including morphometrics and ossification sequence analysis. The results suggest that syndactylous digits evolve as a functional unit; syndactyly may arise through alteration of developmental patterns as suggested by ossification sequence heterochrony. Chapter 7 is a combined analysis of ossification sequences in marsupial and placental postcrania. The results suggest that the special locomotor and developmental requirements on marsupial neonates may metabolically and mechanically impact postcranial ossification patterns, delaying hindlimb development and accelerating ossification of the anterior torso. Chapter 8 summarises the research presented in this thesis and suggests directions for future work on marsupial postcranial evolution, particularly with respect to integrating information on postcranial diversity with ontogenetic work on morphogen expression patterns.
| Identifer | oai:union.ndltd.org:ADTP/258606 |
| Date | January 2008 |
| Creators | Weisbecker, Vera, Biological, Earth & Environmental Sciences, Faculty of Science, UNSW |
| Publisher | Awarded by:University of New South Wales. Biological, Earth & Environmental Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Weisbecker Vera., http://unsworks.unsw.edu.au/copyright |
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