A new small-bodied ornithopod (Dinosauria, Ornithischia) from a deep, high-energy Early Cretaceous river of the Australian–Antarctic rift system

Abstract

A new small-bodied ornithopod dinosaur, Diluvicursor pickeringi, gen. et sp. nov., is named from the lower Albian of the Eumeralla Formation in southeastern Australia and helps shed new light on the anatomy and diversity of Gondwanan ornithopods. Comprising an almost complete tail and partial lower right hindlimb, the holotype (NMV P221080) was deposited as a carcass or body-part in a log-filled scour near the base of a deep, high-energy river that incised a faunally rich, substantially forested riverine floodplain within the Australian–Antarctic rift graben. The deposit is termed the ‘Eric the Red West Sandstone.’ The holotype, interpreted as an older juvenile ∼1.2 m in total length, appears to have endured antemortem trauma to the pes. A referred, isolated posterior caudal vertebra (NMV P229456) from the holotype locality, suggests D. pickeringi grew to at least 2.3 m in length. D. pickeringi is characterised by 10 potential autapomorphies, among which dorsoventrally low neural arches and transversely broad caudal ribs on the anterior-most caudal vertebrae are a visually defining combination of features. These features suggest D. pickeringi had robust anterior caudal musculature and strong locomotor abilities. Another isolated anterior caudal vertebra (NMV P228342) from the same deposit, suggests that the fossil assemblage hosts at least two ornithopod taxa. D. pickeringi and two stratigraphically younger, indeterminate Eumeralla Formation ornithopods from Dinosaur Cove, NMV P185992/P185993 and NMV P186047, are closely related. However, the tail of D. pickeringi is far shorter than that of NMV P185992/P185993 and its pes more robust than that of NMV P186047. Preliminary cladistic analysis, utilising three existing datasets, failed to resolve D. pickeringi beyond a large polytomy of Ornithopoda. However, qualitative assessment of shared anatomical features suggest that the Eumeralla Formation ornithopods, South American Anabisetia saldiviai and Gasparinisaura cincosaltensis, Afro-Laurasian dryosaurids and possibly Antarctic Morrosaurus antarcticus share a close phylogenetic progenitor. Future phylogenetic analysis with improved data on Australian ornithopods will help to test these suggested affinities.

New small-bodied ornithopods (Dinosauria, Neornithischia) from the Early Cretaceous Wonthaggi Formation (Strzelecki Group) of the Australian-Antarctic rift system, with revision ofQantassaurus intrepidusRich and Vickers-Rich, 1999

“…In summary, five ornithopod taxa have been named from the Early Cretaceous of Victoria (Figs. 1.2, 27; Table 5), including: Leaellynasaura amicagraphica and Atlascopcosaurus loadsi from the Eumeralla Formation, known from their maxillae; Qantassaurus intrepidus from the Wonthaggi Formation, known from its dentary; Diluvicursor pickeringi from the Eumeralla Formation, known from a partial postcranium (Herne et al, 2018); and Galleonosaurus dorisae n. gen. n. sp. from the Wonthaggi Formation, known from its maxilla.…”

“…Like Galleonosaurus dorisae n. gen. n. sp., the premaxillary process on the maxilla of Muttaburrasaurus langdoni lacks strong medial inset (unpublished data, Herne and Nair, 2018). However, as in styracosternans, the premaxillary process in M. langdoni is dorsally elevated and a deep channel for the premaxilla is developed on the posterodorsally sloping anterior margin of the anterior ascending ramus (e.g., Norman 2004;Gasulla et al, 2014).…”

Paleontological discoveries in the Chorrillo Formation (upper Campanian-lower Maastrichtian, Upper Cretaceous), Santa Cruz Province, Patagonia, Argentina

“…The proximal end is anteroposteriorly expanded and transversely compressed a condition that was previously considered synapomorphic for Elasmaria by Rozadilla et al (2016Rozadilla et al ( , 2019. However, metatarsal II of Isasicursor is not as expanded anteroposteriorly as in Anabisetia and Diluvicursor (Coria & Calvo, 2002;Herne et al, 2018). The lateral surface of metatarsal II shows a flattened surface for artic- ulation with the medial surface of metatarsal III.…”

“…Distal caudals are indistinguishable from other basal ornithopods (e.g. Gasparinisaura, Anabisetia, Talenkauen, Macrogryphosaurus, Diluvicursor, Sektensaurus, Trinisaura, Jeholosaurus;Coria & Salgado, 1996;Cambiaso, 2007;Calvo et al, 2007;Barrett et al, 2011;Han et al, 2012;Barrett, 2016;Herne et al, 2018;Ibiricu et al, 2019;Rozadilla et al, 2019). Scapula ( Figure 10).…”

Editorial

“…1), with his numerous discoveries recognized by the naming of a new palorchestid, or 'marsupial tapir', Palorchestes pickeringi (Piper 2006). In addition, David's contributions to research on Victorian Cretaceous fossils were recently honoured by the naming of a new ornithopod dinosaur, Diluvicursor pickeringi (Herne et al 2018). Finally, David's professionalism, personal integrity, enthusiasm and affable personality were attributes that made him a pleasure to work with.…”