A second specimen of the Australian cimolodontan multituberculate Corriebaatar marywaltersae from the same locality (Flat Rocks) as the holotype and previously only known specimen, reveals far more anatomical information about the species. The new specimen, composed of most of a dentary containing a complete p4 and alveoli for the lower incisor and the lower first and second molars, exhibits a suite of features consistent with allocation of Corriebaatar to Cimolodonta and further confirms the presence of multituberculates on Gondwana during the Mesozoic. The revised (older) age of the Flat Rocks locality to latest Barremian (mid-Early Cretaceous) establishes C. marywaltersae as the oldest currently known cimolodontan. This has profound biogeographic implications for the distribution of multituberculates on Gondwana as well as globally, particularly in light of the fact that Corriebaatar appears to be a relatively derived member of Cimolodonta.

Key words: Mammalia, Multituberculata, Cimolodonta, Cretaceous, Gondwana, Australia.

Thomas H. Rich [trich@museum.vic.gov.au] and Lesley Kool [koolasuchas@bigpond.com], Museums Victoria, P.O. Box 666, Melbourne, Victoria 3001, Australia. David W. Krause [David.Krause@dmns.org], Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Boulevard, Denver, Colorado 80205, USA; and Department of Anatomical Sciences, Stony Brook University, Stony Brook, New York 11794-8081, USA. Peter Trusler [peter@petertrusler.com.au], School of Earth, Atmosphere & Environment, 9 Rainforest Walk, Monash University, 3800,Victoria, Australia. Matt A. White [fossilised@hotmail.com], University of New England, Armidale, NSW 2350, Australia; and Australian Age of Dinosaurs Museum of Natural History, 1 Dinosaur Way, Winton, Queensland 4735, Australia. Alistair R. Evans [alistair.evans@monash.edu], School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia; and Museums Victoria, P.O. Box 666, Melbourne, Victoria 3001, Australia. Steven Morton [steven.morton@monash.edu], School of Physics and Astronomy, Monash University, Victoria 3800, Australia. Patricia Vickers-Rich [pat.rich@monash.edu; prich@swin.edu.au], School of Earth, Atmosphere and Environment, Monash University, Victoria 3800; and Department of Chemistry and Biotechnology, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia.