Studies in New Zealand Cretaceous Mollusca

Abstract

A complete taxonomic revision of ammonites from the Mata Series (Santonian-Maastrichtian) of New Zealand is presented. One genus and thirteen species previously established for New Zealand ammonites of this age are considered to be junior synonyms. A new diplomocerid genus, Masonites, and sixteen new species, Glyptoxoceras kotakai, Masonites biannulatus, Pseudoxybeloceras compressum, P. bistriatum, Kossmaticeras (Natalites) bensoni Jacobites (Jacobites) flexistriatus, J. (J.) maximus, J. (J.) stevensi, J. (J.) quadratus J. (J.) marwicki, Maorites angulostriatus, M. multiconstrictus, Gunnarites spathi, G. varistriatus, Neograhamites transitorius and Eupachydiscus depressus are proposed. Representatives of Neograhamites, Eupachydiscus and Anapachydiscus are recorded from New Zealand for the first time. The biostratigraphy of Mata ammonite taxa is poorly known but it is thought that two stratigraphically and faunally distinct assemblages, one characteristic of the Lower Piripauan Stage and the other characteristic of the Upper Piripauan and Haumurian Stages, can be differentiated. Faunal relationships of the Mata assemblages are discussed in terms of the world ammonite faunal provinces and migrations for Santonian-Maastrichtian time. Correlation by ammonites of the Mata Series with the standard Cretaceous succession in Europe is reviewed. The Upper Piripauan and Haumurian Stages are considered to be correlatives of the Campanian and Maastrichtian and the Lower Piripauan is thought to be a correlative of the Santonian.