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.

http://zoobank.org/urn:lsid:zoobank.org:pub:68553D05-C54C-4EFE-AF08-C7E4A17E5B0C

摘要

两种bulimoid 陆地蜗牛，Maoristylus pliocenicus n。sp。和Archaeostylus n。将军 manukauensis n. sp.，在 Botriembryontidae 亚科 Placostylinae 中，是从新西兰北部 Māngere 的地下 Kaawa 组贝壳沉积物中回收的化石贝壳中描述的。这些化石属于上新世晚期（Waipipian Stage [latez Zanclean-early Piacenzian]，3.7-3.0 Ma），是已知的最古老的 Placostylinae 代表。相关的化石动物群表明陆地蜗牛壳沉积在沿海入口的浅潮下深度。Mauristylus pliocenicus n. sp。具有高度独特的皱纹雕塑，在这方面与现代非常相似来自豪勋爵岛的M. etheridgei (Hedley, 1891)。后一个分类群被描述为M. bivaricosus的一个亚种（Gaskoin ，1855），但由于其独特的壳形态，它在这里被视为一个单独的物种。Archaeostylus n. 将军 manukauensis n. sp。具有与 Placostylinae 中的其他分类群明显不同的孔径形态。它可能属于一个姐妹谱系，而不是现存分类群的祖先。它和M. pliocenicus n. sp。在最近的上新世或更新世时期，新西兰的血统已经灭绝，这可能是气候变冷的结果。

http://zoobank.org/urn:lsid:zoobank.org:pub:68553D05-C54C-4EFE-AF08-C7E4A17E5B0C