Author(s) |
Mitchell, David Rex
Wroe, Stephen
Sherratt, Emma
|
Publication Date |
2019-03-11
|
Abstract |
<p>The structure and material properties of different foods are widely considered to be
reflected in the mechanics of the vertebrate skull. In this thesis, the relationship between
feeding ecology and cranial morphology is examined in extant kangaroos and relatives.
Geometric Morphometrics (3D shape analysis) and Finite Element Analysis (a form of
computational biomechanics) were employed in order to identify the influences that the
physical properties of vegetation, and behaviours involving food procurement, have on the
shape and structure of the cranium. </p>
<p>The thesis focusses on the Macropodiformes, a sub-order of herbivorous diprotodont
marsupials that includes three extant families: kangaroos and wallabies (Macropodidae),
bettongs, potoroos, and rat-kangaroos (Potoroidae), and the musky rat-kangaroo
(Hypsiprymnodontidae). This clade is represented by a diverse array of extant species from
which to draw known ecology and diet across a broad range of body sizes. An initial
interspecific study on sixteen macropodiform species found that feeding ecology is clearly
associated with the relative lengths of the muzzle and zygomatic arch. Species that bite harder
with the anterior dentition on more resistant foods possess a shorter muzzle and longer
zygomatic arch.</p>
<p>By applying these methods to three closely related pademelon (genus: <i> Thylogale</i>) taxa,
biomechanical performance during anterior biting was also found to reflect the mechanical
properties of their respective diets at the subspecies scale. A diet dominated by more resistant
vegetation was again represented by a shorter, more robust cranium, while a longer, more gracile cranium was observed in species that either bite into softer foods or employ cervical
musculature to obtain more vegetation via tension (plucking), thus not requiring harder bites.</p>
<p>Wombats and koalas were then incorporated into a sample of other medium to large
macropodiform species to test the viability of these previous findings at a broader scale. The
results were then used to suggest the potential feeding ecology of an extinct species: the giant
short-faced kangaroo, <i>Simosthenurus occidentalis</i>. Diet was clearly associated with palatodental
arrangement across these species. However, muzzle length was not determined by diet, as in
the previous chapters, but rather was associated with the hardest bites required of a species
within its particular niche. A combination of cranial features and dental arrangements indicate
that <i>S. occidentalis</i> was likely a browser, capable of consuming tough, bulky vegetation. </p>
<p>The findings of this thesis suggest that craniofacial morphology is intimately linked with
dietary ecology among these species and may be used to infer the potential feeding behaviours
and diet of rare or remote marsupial herbivore species for conservation and management
strategies and also of extinct species for inferring their paleoecology. The relationships
identified here could be applicable to other herbivorous taxa and used in tandem with
microwear and stable isotope analyses to draw more robust conclusions, regarding feeding
ecology and behaviour. </p>
|
Link | |
Publisher |
University of New England
|
Title |
The cranial mechanics of herbivory in kangaroos and relatives: an integrated geometric morphometric and finite element approach
|
Type of document |
Thesis Doctoral
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Entity Type |
Publication
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