Taxonomy and taphonomy of Pliocene bulimoid land snails from Māngere, northern New Zealand, with descriptions of a new genus and two new species (Gastropoda: Bothriembryontidae: Placostylinae)

Abstract

ABSTRACT Two species of bulimoid land snails, Maoristylus pliocenicus n. sp. and Archaeostylus n. gen. manukauensis n. sp., in family Bothriembryontidae, subfamily Placostylinae, are described here from fossil shells that were recovered from subsurface Kaawa Formation shelly sediments at Māngere, northern New Zealand. These fossils are of late Pliocene age (Waipipian Stage [latest Zanclean-early Piacenzian], 3.7–3.0 Ma), and are the oldest known representatives of the Placostylinae. The associated fossil fauna indicates that the land snail shells were deposited at shallow subtidal depths in a coastal inlet. The teleoconch of Maoristylus pliocenicus n. sp. has highly distinctive rugose sculpture and in this regard is very similar to modern M. etheridgei (Hedley, 1891) from Lord Howe Island. The latter taxon was described as a subspecies of M. bivaricosus (Gaskoin, 1855), but it is here treated as a separate species on account of its distinctive shell morphology. Archaeostylus n. gen. manukauensis n. sp. has apertural morphology that differs markedly from other taxa in Placostylinae. Rather than being ancestral to extant taxa it probably belonged to a sister lineage. Both it and the M. pliocenicus n. sp. lineage went extinct in New Zealand during latest Pliocene or Pleistocene time, possibly as a consequence of a cooling climate.