Parahyotissa (Parahyotissa) inermis (G.B. Sowerby II, 1871 )

Raines, Bret & Huber, Markus, 2012, 3217, Zootaxa 3217, pp. 1-106 : 26-27

Parahyotissa (Parahyotissa) inermis (G.B. Sowerby II, 1871)

Figures 12 A–I

Ostrea inermis G.B. Sowerby II, 1871 : sp. 82, pl. 28, fig. 82.

Ostrea imbricata Lamarck, 1819: p 213 , non Gmelin, 1791.

? Parahyotissa numisma (Lamarck) — DiSalvo et al., 1988: p. 459.

Ostrea — Luke, 1995: p. 106.

Parahyotissa (Parahyotissa) inermis (G.B. Sowerby II, 1871) — Huber, 2010: p. 185, figs. 2–3; Severns, 2011: p. 464, pl. 212, fig. 4.

Material examined. More than a dozen single valves (up to ca. 33 mm) (BK), including several valves collected by the 1957/58 Downwind Expedition ( SIO Benthic Collection, M1438 and M1451).

Diagnosis. Shell medium to large, irregularly shaped, ovate-subovate, rather thin and somewhat fragile. Exterior surface of 9–12 radial plicated folds, which may be angular or rounded with flattened spines, and dense overlapping commarginal lamellae. Interior nacreous, with a yellowish-white ventral margin. Hinge stout with numerous vermicular chomata, marginally placed ( Fig. 12 E). Characteristic vesicular (honeycomb) sculpture. Color extremely variable, from creamy white to dark yellow, brownish purple, or reddish.

Remarks. The Parahyotissa numisma (Lamarck) recorded by DiSalvo et al. (1988) cannot be confirmed. Unfortunately, it was one of the few specimens which DiSalvo had misplaced and was unable to provide it for our study. However, in all likelihood it was P. inermis which he had actually found. The ‘ Ostrea ’ specimens noted by Luke (1995) from the SIO Benthic Collection, M1438 and M1451 ( Figs. 12 F–I) are not Ostrea , but is P. inermis as well.

Kirkendale et al. (2004) proposed the synonymy of genus Parahyotissa with Hyotissa Stenzel, 1971 . We do not accept the species or the specimens analyzed as sufficient basis for such a substantial change. Apart from the very limited material analyzed, none of the specimens were from their type localities. Furthermore, some of the more taxonomically important species were not addressed at all; not Hyotissa fisheri ( Dall, 1914) , Hyotissa sinensis ( Gmelin, 1791) , or Hyotissa fusca ( Lamarck, 1819) . Also not included, was the most common Indo-Pacific species Parahyotissa inermis (G.B. Sowerby II, 1871) , nor the Panamic Parahyotissa quercina (G.B. Sowerby II, 1871) . Until a wider analysis is presented, Harry’s 1985 original arrangement is being followed.

Habitat. Commonly found at many locations around EI, dead in sand, from 30–100 m.

Distribution. Parahyotissa inermis is a widely distributed species from eastern Africa to the Hawaiian Islands, but not known from New Zealand or the Kermadec Islands. Now reported from Easter Island— E5.