An ancyloceratid ammonite from the Aptian Maryborough Formation, Queensland, Australia, and synonymy of Australiceras Whitehouse with Tropaeum Sowerby

Abstract

McKENZIE, E.D., ROZEFELDS, A.C., DEACON, P., 2014. An ancycloceratid ammonite from the Aptian Maryborough Formation, Queensland, Australia, and synonymy of Australiceras Whitehouse with Tropaeum Sowerby. Alcheringa 38. ISSN 0311–5518.This first description and illustration of ammonites from the Maryborough Formation on Woody Island, Hervey Bay in Queensland shows that all known specimens are referable to Tropaeum jackii (Etheridge Jr 1880) comb. nov., for which a neotype is, herein, nominated to replace the missing lectotype. An analysis of comparative material from other eastern Australia Cretaceous basins, including the type specimens of Australiceras, illustrates that the variability of tuberculation can not be used to separate genera, nor species. Australiceras Whitehouse, 1926 is considered a junior synonym of Tropaeum J. de C. Sowerby. Two other Australiceras species are also transferred to Tropaeum; T. lampros (Etheridge Jr) comb. nov. and T. irregulare (Tenison Woods) comb. nov. The changing patterns, throughout ontogeny, of lateral rib densities (herein defined) and whorl shapes are useful for distinguishing these species. As the ammonites from the Maryborough Formation all fit within the present definition of Tropaeum jackii, and as this has been defined as a late Aptian taxon by faunal studies supported by extensive palynological work in adjacent Australian Cretaceous basins, the ammonites provide support for the assignment of a late Aptian age to this part of the formation.E.D. McKenzie [edmck@bigpond.com] and A.C. Rozefelds [andrew.rozefelds@qm.qld.gov.au] Queensland Museum, GPO Box 3300, South Brisbane, 4101, Queensland, Australia; Paula Deacon, [Paula.Deacon@dnrm.qld.gov.au] Geological Survey of Queensland, Department of Natural Resources and Mines (DNRM), PO Box 15216, City East, 4002, Queensland, Australia. Received 24.12.2012, revised 14.10.2013; accepted 28.10.2013.