Diluvicursor pickeringi: A small-bodied Ornithopod Dinosaur from the Early Cretaceous of Victoria, Australia.

The southern portion of Victoria State in Australia contains extensive deposits laid down in the Early Cretaceous, when the area was part of a rift valley system formed as Australia separated from Antarctica. This region had a rich terrestrial biota inhabiting a series of river floodplains, with a high input of volcanic material. These deposits have produced a wide range of Vertebrate fossils, including Temnospondyl Amphibians, Ornithischian and Theropodan Dinosaurs, Multituberculate, Monotreme and Tribosphenic Mammals, Plesiosaurs, Pterosaurs and Chelonians.

In a paper published in the journal PeerJ on 11 January 2018, Matthew Herne of the School of Biological Sciences at The University of Queensland, Alan Tait of the School of Earth, Atmosphere and Environment at Monash University, Vera Weisbecker, also of the School of Biological Sciences at The University of Queensland, Michael Hall, also of the School of Earth, Atmosphere and Environment at Monash University, Jay Nair, again of the School of Biological Sciences at The University of Queensland, Michael Cleeland of the Bunurong Environment Centre, and Steven Salisbury, once again of the School of Biological Sciences at The University of Queensland, describe a new species of small-bodied Ornithopod Dinosaur from the Early Cretaceous Eumeralla Formation of Victoria, Australia.

The new species is named Diluvicursor pickeringi, where 'Diluvicursor' means 'flood-runner' in reference to the deposits in which it was found, which are interpretted as having been laid down in a deep scour-channel in a fast moving river, and 'pickeringi' honours the late David Pickering for his contributions to the palaeontology of Australia. It is described from a single, partial specimen comprising the tail and right foot from a Dinosaur somewhere between the size of that of a Turkey and that of a Rhea.

Diluvicursor pickeringi, as prepared on five blocks of sandstone. (A) Specimen viewed from above, normal to the bedding. (B) Schematic. Abbreviations: as, astragalus; B #, host block number; Ca #, designated caudal vertebra and position; cal, calcaneum; fib, fibula; ha #, haemal arch/process and position; pd #, pedal digit number; tib, tibia. Stephen Poropat/Museums Victoria in Herne et al. (2018).

The specimen was located within the Eric the Red West Sandstone member, which is interpreted as a deep scour channel laid down within a wide, fast moving river. This bed contains a large amount of woody material, which suggests that the river was running through a forested terrain, and has produced fossils of Fish, Chelonians, Plesiosaurs, Pterosaurs, small Ornithischians, Theropods and Mammals, though most of these are yet to be formally described.

Artist’s interpretation of the early Albian, volcaniclastic, floodplain palaeoenvironment within the Australian-Antarctic rift graben, in the region of Eric the Red West. Scene depicting two individuals of Diluvicursor pickeringi on the cutbank of a high-energy meandering river, regional floral components and distant rift margin uplands. Floral components potentially included forest trees of Araucariaceae (Agathis and Araucaria), Podocarpaceae and Cupressaceae and lower story/ground cover plants, including Pteridophytes (Ferns, including Equisetaleans), Hepatics, Lycopods, Cycadophytes, Bennettitaleans, Seed-bearing Fern- or Cycad-like Taeniopterids and early Australian Angiosperms. Peter Trusler in Herne et al. (2018).

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An Australian Spinosaurid

In May this year (2011) a team lead by Paul M. Barrett of the Department of Palaeontology at the Natural History Museum in London published a paper in the journal Biology Letters in which they report the discovery of a single cervical vertebra (neck bone) of a spinosaurid dinosaur from the Early Cretaceous of Victoria, Australia. This is the first reported discovery of a spinosaurid dinosaur in Australia.

The Spinosaurid cervical vertebrae. Scale bar = 20 mm.

The spinosaurids are an unusual group of theropod dinosaurs with narrow elongate snouts that have been compared to those of crocodiles. Palaeobilologists have suggested that they may have fed in a similar way to modern crocodiles, preying on fish and small animals in an aquatic environment. Isotopic studies of the bones of spinosaurs have also suggested they spent much of their time in the water. The group takes its name from the first species discovered, Spinosaurus, which had elongate spines on its thoracic vertebrae (back bones), although these spines have not been found in other species, so the name is slightly misleading. It is theorized that the spines in Spinosaurus supported either a sail-like structure (popular with dinosaur artists and the popular press) or a camel-like hump (popular with palaeobiologists).

An artist's impression of Spinosaurus by dinosaur artist and palaeontologist Lukas Panzarin.

The spinosaurs belong to a larger group of theropod dinosaurs called the Megalosauroidea, which groups them with the megalosaurs (unsurprisingly) and a few other species that are apparently closer to these two groups than they are to the Avetheropoda, the group which includes allosaurs and birds. The spinosaurs appeared in the mid Jurassic and became fairly abundant in the early Cretaceous. They are not known from the later Cretaceous, though some isolated teeth of possible spinosau origin have been found.

The Australian specimen closely resembles a neck vertebrae from Baryonyx walkeri, a species known from the Early Cretaceous Wealden Beds of Southern England, though sensibly Barrett et al. have not attempted to assign a species to this single bone. A Baryonyx specimen from the Wealden beds was found with fish scales in its stomach, further supporting the aquatic lifestyle theory for spinosaurs.

An impression of Baryonyx walkeri by dinosaur artist Adam Stuart Smith.

The specimen was discovered in the Eumeralla Formtion, part of the Early Cretaceous Otway Group, to the east of Crayfish Bay, Victoria. The Eumeralla Formation is a series of mudstones, siltstones and volcanogenic sandstones, thought to represent a floodplain with meandering rivers, swampland and many shallow lakes.

Barrett et al. also note that the absence of spinosaurs, and other groups, from Australia has been used in the past to support theories about the break up of the ancient supercontinent of Gondwana, on the basis that groups absent from a particular chunk of the former landmass indicate that the piece in question had split off from the main before that species had emerged. Barrett et al. dismiss this approach since as we discover more about ancient faunas, we increasingly find species in places where we had thought that they were absent, and that even if we do not find evidence for the presence of a species, that does not mean it was not there.

See also The Ashdown Maniraptoran,
Head-Butting in a Pachycephalosaur
and Dinosaurs on Sciency Thoughts YouTube.