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Geochronology, taxonomy and morphology of select fossils of the Buchan Caves, south-eastern Australia
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posted on 09.11.2017by Danielle A. Shean
The Buchan Caves, in the northeast of Victoria, contain
a diverse and fascinating palaeofauna, reflecting a wide range of
environmental conditions from the Pleistocene through to the present.
Prominent within the assemblage is the Pleistocene-aged megafauna,
represented at Buchan by Thylacoleo carnifex, Simosthenurus
occidenta/is, 'Procoptodon' gilli, Zygomaturus trilobus, Diprotodon
optatum, Protemnodon anak, Protemnodon sp., Sthenurus sp., Palorchestes
azael and Palorchestes parvus. The objective of this thesis was to
investigate the antiquity, morphology and myology of a newly discovered
cranium of Palorchestes azael. Using Uranium-Thorium dating technique on
calcite encrusting the fossil, a new date of 275 ± 0.03 Ka was
determined, which allows correlation of this fossil locale with other
fossiliferous cave deposits throughout Australia. Examination of
comparative myology and osteology of vestibular-proboscis-bearing
placental mammals, including Tapirus terrestris, Elephas maximus, Saiga
tatarica andAlces alces, it is suggested that unlike older species
within the genus, such as P painei, P azael did not possess a proboscis.
Distinct differences in cranial morphology (such as the unusual
positioning of the jugal, nasals and zygomatic arch, as well as
foreshortening of the antero-dorsal surface of the cranium) indicates
that P azael differs from all other species observed in this
investigation. The differences observed in the masticatory musculature
proposed a change in dietary behaviour from older species of
Palorchestes. The large sinus cavities observed throughout the cranium
of P azael are structurally analogous to those of Diprotodon optatum, a
contemporary of P azael, and may represent a functional multi-derived
feature, possibly evolved to reduce skull weight and increase surface
area for the insertion of masticatory musculature.