MAASTRICHTIAN SCAPHOPODA AND GASTROPODA FROM THE MIRIA FORMATION, CARNARVON BASIN, NORTHWESTERN AUSTRALIA

WA Museum Records and Supplements | Updated 9 years ago

Abstract: One scaphopod and 35 gastropod species are recorded from the Late Maastrichtian Miria Formation of the Carnarvon Basin, northwestern Australia. Preservation of the fossils suggests that the assemblage, which is inferred to contain herbivores, possible detrital feeders, graz.ers, predatory and ectoparasitic carnivores, is only partly representative of the original fauna. The original mineralogy of the shells has, in part, determined which mollusks have been preserved, their state at recovery, and whether or not they can be identified. Primary calcite has remained but argonite has been lost and partially replaced by secondary calcite. Six species are known only from internal moulds,

Five new species - Conotomaria millacis sp. nov., Conolomaria (?) cypsela sp. nov., Leptomaria perancisa sp. nov., Nododelphinula dracontis sp. nov., and Euthriofusus (?) vandegraaffi sp. nov. are described and named. The order of abundance is Neotaenioglossa > Archaeogastropoda > Neogastropoda > Heterobranchia > Opisthobranchia. Four species remain indeterminable.

All genera recognized were widely distributed in the combined Tethyan - Temperate Realms of the Late Cretaceous; some possible Tethyan elements are, at most, weakly represented. Two species are very close to described European taxa of the Late Cretaceous and two others are very close to described North American species. Affinities with the faunas of South India, Natal and Malagasy appear to be weak.

No generic endemism is noted among the gastropods and there is no support from this group for the concept of a faunal subprovince in the region during the Late Cretaceous. The climatic regime indicated by the gastropods is considered to have been temperate as was concluded from our previous study of the Bivalvia. Most of the species persisted to the Cretaceous Tertiary boundary.