Three new species of the family Neolepetopsidae from hydrothermal vents and whale falls in the northeastern Pacific

Journal of Shellfisheries Research, March, 2008 by James H. McLean

ABSTRACT Three new northeastern Pacific species of the deep-sea limpet family Neolepetopsidae are described. One (Paralepetopsis tunnicliffae) is from the hydrothermal vent habitat, and two (Paralepetopsis clementensis and Neolepetopsis nicolasensis) are from whale bone. This is the first record of the genus Paralepetopsis from the eastern Pacific, and the first record of the family from whale bone, in contrast to all previous records from hydrothermal vents and seeps. The family Neolepetopsidae joins the cocculiniform Pyropeltidae in its occurrence in the vent/seep habitat and the whale-fall habitat. Unlike the Pyropeltidae, in which species may occur in both the vent/seep and the whale-fall habitat, the two new neolepetopsid species in the whale-fall habitat are not the same as the species in the nearest vent/seep habitats.

KEY WORDS: hydrothermal vents, whale-falls, new species, northeastern Pacific Neolepetopsidae

INTRODUCTION

The family Neolepetopsidae was proposed some 18 years ago (McLean 1990), at which time I proposed higher levels of classification for this family, arguing that it represented a basal sister group to all other patellogastropods. Fretter (1990) provided a report on the anatomy, finding it not unlike other patellogastropods except for the radula. Subsequently, Lindberg (1998) treated it as the most apomorphic family in Acmaeoidea; more recently, Waren & Bouchet (2005) have reinstated it at a higher level and have recognized it as the superfamily Neolepetopsoidea. Sasaki & Waren (2007, abstract), have suggested "possible relationships with deep-sea Acmaeoidea." Kiel (2004) reported that the outer layer of neolepetopsid shell structure is "prismatic complex crossed lamellar," a combination shown by Hedegaard (1990) to be entirely calcitic. This was considered by Kiel to provide "further evidence for their position as sister group of the Acmaeidae." My original observation (McLean 1990) was that the individual teeth of the radula of the Neolepetopsidae were unmineralized, considering that the teeth are not darkly opaque, as observed in the shallow-water patellogastropods. However, Cruz & Farina (2005), have shown that the teeth are in fact mineralized, making them less unique than they may seem to be.

Additional species of Neolepetopsidae have been described by Beck (1996) and by Waren & Bouchet (2001). Beck extended the distribution to the Edison Seamount in the western Pacific with the description of Paralepetopsis rosemariae. Waren & Bouchet (2001) provided notes on eastern Pacific species of Neolepetopsis, and described two additional species of Paralepetopsis: P. ferrugivora, from the Mid-Atlantic Ridge and P. lepichoni from the Nankai Trench, off Southeastern Honshu, Japan.

Here I take the opportunity to describe three additional northeastern Pacific species of the family Neolepetopsidae, including two species of the genus Paralepetopsis and one new species of Neolepetopsis. One of the species, a new Paralepetopsis, is from the hydrothermal vent habitat; another new Paralepetopsis and a new Neolepetopsis are from whale bone, which is an hitherto unknown habitat for the family, although the whale bone habitat is known for the cocculiniform families Pyropeltidae, Cocculinidae (see McLean 1992), and Osteopeltidae (see Marshall 1994). Only the family Pyropeltidae has previously been known from both the vent/seep and whale bone habitat.

METHODS

Shells of the new species were photographed with three views. The radula from the single specimen of Paralepetopsis tunnicliffae was mounted for SEM; radulae of the two other new species were whole-mounted in stain-suffused, nonresinous mounting medium. For these two new species, the entire radular ribbon was digitally photographed through a light microscope, which enabled a count of the tooth rows and, at higher resolution enabled confirmation of the generic identification indicated by the shell morphology.

Specimens are deposited in the type collection of the Natural History Museum of Los Angeles County (LACM).

SYSTEMATICS

Family Neolepetopsida (McLean, 1990)

Genus Neolepetopsis (McLean 1990)

Neolepetopsis McLean, 1990: 492. Type species (OD): Neolepetopsis gordensis McLean, 1990. Type locality: Escanaba Trough, Gorda Ridge, off northern California (41[degrees]29'N, 128[degrees]29'W), 3,271 m.

Shell sculpture coarsely clathrate, shell interior with transparent zones. Radula with well-formed rachidian, two pairs of laterals, paired pluricuspid teeth, and two pairs of marginals.

Four species, all from abyssal depths at hydrothermal vents, were originally described by McLean (1990). Two of these species, N. verruca from the East Pacific Rise at 21[degrees]N, and N. occulta from the Green Seamount at 21[degrees]N have not been subsequently reported. The species N. densata from the East Pacific Rise at 12[degrees]N was reported by Gustafson & Lutz (1994) from the Galapagos Rift; Waren & Bouchet (2001) illustrated the shell and radula of N. densata, with figures that closely matched my original figures.