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Megaraptorid theropod material from Early Cretaceous of Australia
A new online paper:
Phil R. Bell, Andrea Cau, Federico Fanti & Elizabeth Smith (2015)
A large-clawed theropod (Dinosauria: Tetanurae) from the Lower
Cretaceous of Australia and the Gondwanan origin of megaraptorid
Gondwana Research (advance online publication)
New megaraptorid material is described from the Early Cretaceous of Australia.
The unnamed taxon represents the largest Australian theropod.
Palaeobiogeographic assessment supports an Australian origin for Megaraptoridae
The traditional concept of an Australian refugium for relict taxa is challenged.
Megaraptoridae comprises a clade of enigmatic Gondwanan theropods with
characteristic hypertrophied claws on the first and second manual
digits. The majority of megaraptorids are known from South America,
although a single genus (Australovenator) plus additional
indeterminate material is also known from Australia. This clade has a
controversial placement among theropods, and recently has been
interpreted alternatively as a carcharodontosaurian or a
tyrannosauroid lineage. We describe new fragmentary but associated
postcranial remains from the opal fields of Lightning Ridge
(middle-Albian, Griman Creek Formation) in north-central New South
Wales. The new unnamed taxon exhibits a number of unusual features
that suggest the presence of a hitherto unrecognized Australian
megaraptorid. From an Australian perspective, the Lightning Ridge
taxon predates Australovenator by c.10Ma and is minimally coeval with
megaraptoran material reported from the Eumeralla Formation of
Victoria (but potentially 6.1–9.5 Ma younger). It is also notable as
the largest predatory dinosaur yet identified from Australia and is
only the second theropod known from more than a single element. A
Bayesian phylogenetic approach integrating morphological,
stratigraphic and palaeogeographic information tested both the
carcharodontosaurian and tyrannosauroid placements for Megaraptora.
Regardless of the preferred placement among Tetanurae, rigorous
palaeobiogeographic analyses support an Asian origin of Megaraptora in
the latest Jurassic (about 150-135 Ma), an Early Cretaceous (about
130-121 Ma) divergence of the Gondwanan lineage leading to
Megaraptoridae, and an Australian root for megaraptorid radiation.
These results indicate that Australia’s Cretaceous dinosaur fauna did
not comprise simply of immigrant taxa but was a source for complex
two-way interchange between Australia-Antarctica-South America leading
to the evolution of at least one group of apex predatory dinosaurs in