A polar dinosaur-track assemblage from the Eumeralla Formation (Albian), Victoria, Australia

Abstract

Martin, A.J., Rich, T.H., Hall, M., Vickers-Rich, P. & Vazquez-Prokopec, G., June 2012. A polar dinosaur-track assemblage from the Eumeralla Formation (Albian), Victoria, Australia. Alcheringa 36, 171–188. ISSN 0311-5518. The Eumeralla Formation (Aptian–Albian) of the Otway Group in Victoria, Australia, has yielded a significant amount of dinosaur skeletal material since the late 1970s, which, when combined with finds from the Wonthaggi Formation (Aptian) of the upper Strzelecki Group, constitute the best-documented polar-dinosaur assemblage in the Southern Hemisphere. In contrast, dinosaur tracks have barely augmented this body fossil record; up to now, only one ornithopod track had been documented in any detail from the Otway Group. In this study, we report a new find of at least 24 dinosaur tracks preserved on two ripple-bedded sandstone blocks of the Eumeralla Formation, discovered at Milanesia Beach, Victoria. This dinosaur-track assemblage is the best in terms of numbers and quality found thus far in formerly polar environments of the Southern Hemisphere. One block includes the first known dinosaur trackway from the Cretaceous of Victoria, consisting of three consecutive footprints made by a small theropod. The assemblage indicates three differently sized theropods, thus providing new insights on dinosaur diversity and activity not indicated previously by body fossils in the Eumeralla Formation. Tracks are preserved in fluvial floodplain deposits and were possibly imprinted on emergent floodplain surfaces following seasonal flooding during a polar summer. The abundant tracks at this site suggest more such finds are likely in floodplain deposits of the Otway Group, although behavioural and preservational conditions unique to polar environments may have limited their formation. Anthony J. Martin and Gonzalo Vazquez-Prokopec [geoam@learnlink.emory.edu, gmvazqu@emory.edu] Department of Environmental Studies, Emory University, Atlanta, GA 30322, USA; Thomas H. Rich [trich@museum.vic.gov.au] Museum Victoria, Melbourne, Victoria, Australia; Michael Hall, Patricia Vickers-Rich and secondary address of Anthony J. Martin [mike.hall@monash.edu, pat.rich@monash.edu] School of Geosciences, Monash University, Clayton, Victoria 3800, Australia. Received 15.4.2011; revised 6.6.2011; accepted 14.6.2011.