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Theropod fauna from Southern Australia
From: Ben Creisler
A new paper in PLoS ONE:
Benson, R.B.J., Rich, T.H., Vickers-Rich, P. & Hal,l M, (2012)
Theropod Fauna from Southern Australia Indicates High Polar Diversity
and Climate-Driven Dinosaur Provinciality.
PLoS ONE 7(5): e37122.
The Early Cretaceous fauna of Victoria, Australia, provides unique
data on the composition of high latitude southern hemisphere
dinosaurs. We describe and review theropod dinosaur postcranial
remains from the Aptian–Albian Otway and Strzelecki groups, based on
at least 37 isolated bones, and more than 90 teeth from the Flat Rocks
locality. Several specimens of medium- and large-bodied individuals
(estimated up to ~8.5 metres long) represent allosauroids.
Tyrannosauroids are represented by elements indicating medium body
sizes (~3 metres long), likely including the holotype femur of Timimus
hermani, and a single cervical vertebra represents a juvenile
spinosaurid. Single specimens representing medium- and small-bodied
theropods may be referrable to Ceratosauria, Ornithomimosauria, a
basal coelurosaur, and at least three taxa within Maniraptora. Thus,
nine theropod taxa may have been present. Alternatively, four distinct
dorsal vertebrae indicate a minimum of four taxa. However, because
most taxa are known from single bones, it is likely that small-bodied
theropod diversity remains underestimated. The high abundance of
allosauroids and basal coelurosaurs (including tyrannosauroids and
possibly ornithomimosaurs), and the relative rarity of ceratosaurs, is
strikingly dissimilar to penecontemporaneous dinosaur faunas of Africa
and South America, which represent an arid, lower-latitude biome.
Similarities between dinosaur faunas of Victoria and the northern
continents concern the proportional representatation of higher clades,
and may result from the prevailing temperate–polar climate of
Australia, especially at high latitudes in Victoria, which is similar
to the predominant warm–temperate climate of Laurasia, but distinct
from the arid climate zone that covered extensive areas of Gondwana.
Most dinosaur groups probably attained a near-cosmopolitan
distribution in the Jurassic, prior to fragmentation of the Pangaean
supercontinent, and some aspects of the hallmark ‘Gondwanan’ fauna of
South America and Africa may therefore reflect climate-driven
provinciality, not vicariant evolution driven by continental
fragmentation. However, vicariance may still be detected at lower