New Early Paleocene Mollusca from the Wangaloa Formation of South Island, New Zealand

Abstract

New Mollusca from the shallow marine, highly fossiliferous Wangaloa Formation of southeastern Otago, South Island, New Zealand, are described. This paper reports three new species and one new genus: Leionucula palaioanaxea n. sp. of the Nuculidae, Pyropsis zinsmeisteri n. sp. of the Tudiclidae, and Wangacteon grebneffi n. gen. and sp. of the Acteonidae. These taxa represent new records in New Zealand of apparently endemic taxa. The molluscan fauna of the Wangaloa Formation is important in the understanding of Paleogene biogeography of the Southern Hemisphere and changes in faunal composition of the Cretaceous–Tertiary Gondwana Realm. Genus- and species-level endemism in the “Wangaloan” fauna is marked and is probably a reflection of “greater New Zealand” 's geographic and genetic isolation during the Paleocene. Although deposits containing early Paleogene Mollusca are generally rare in the Southern Hemisphere, comparisons of known Gondwana molluscan taxa and those of similar age in the Northern Hemisphere indicate that the Mollusca of the Wangaloa Formation have Early Paleocene affinities. Microfossil evidence, in addition, supports an Early Paleocene age for the fauna. However, an uppermost Cretaceous age is indicated for the basal part of the Wangaloa Formation stratigraphically below the shell beds, but the K–T boundary has yet to be located.