A rare and unusual new bittiine genus with two new species from the South Pacific (Cerithiidae, Gastropoda).

Ellen E Strong,Philippe Bouchet

doi:10.3897/zookeys.758.25100

Abstract

A new genus, Limatium gen. n., and two new species, L. pagodula sp. n. and L. aureum sp. n. are described, found on outer slopes of barrier reefs and fringing reefs in the South Pacific. They are rare for cerithiids, which typically occur in large populations. The two new species are represented by 108 specimens sampled over a period of 30 years, only 16 of which were collected alive. Three subadults from the Philippines and Vanuatu likely represent a third species. In addition to their rarity, Limatium species are atypical for cerithiids in their smooth, polished, honey to golden brown shells with distinctive white fascioles extending suture to suture. The radula presents a unique morphology that does not readily suggest an affinity to any of the cerithiid subfamilies. Two live-collected specimens, one of each species and designated as holotypes, were preserved in 95% ethanol and sequenced. Bayesian analysis of partial COI and 16S rDNA sequences demonstrates a placement in the Bittiinae, further extending our morphological concept of the subfamily.

Highlights

The Cerithiidae is one of 19 families of Cerithioidea currently accepted, and with 219 species considered valid, it is one of the most diverse (Bouchet et al 2017, MolluscaBase 2018)
Houbrick’s (1993) generic review of the Bittiinae published 25 years ago remains the authoritative resource for comparative anatomy and systematics of bittiines
Houbrick (1993) recognized nine genera in the Bittium-group: Bittium, Argyropeza, Bittiolum, Cacozeliana, Ittibittium, Lirobittium, Neostylidium [ as Stylidium], Varicopeza, and Zebittium; Cassiella was identified as a possible member but its placement uncertain given the paucity of anatomical data

Summary

Introduction

The Cerithiidae is one of 19 families of Cerithioidea currently accepted, and with 219 species considered valid, it is one of the most diverse (Bouchet et al 2017, MolluscaBase 2018). Collections were represented mainly by empty shells, with only a handful of live-collected specimens that had been subsequently dried. This hampered the use of anatomical dissections to explore their systematic placement; the unique radula did not suggest an affinity to any of the cerithiid subfamilies. In 2013 a specimen of a second species was preserved for molecular analysis during the TUHAA PAE 2013 cruise to the Austral Islands. Based on this material, we here describe a new genus, Limatium n. We here describe a new genus, Limatium n. gen., with two new species, L. pagodula sp. n. and L. aureum sp. n

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