Cryptogemma phymatias, (WATSON, 1886)

CRYPTOGEMMA PHYMATIAS (WATSON, 1886) View in CoL

( FIG. 6)

Pleurotoma phymatias R. B. Watson, 1886 . 1920 m, Philippine Islands, 16°42′N, 119°22′E (Expedition H.M.S. Challenger on 13 November 1874, st. 205).

Gemmula benthima Dall, 1908 . 2323 m, Gulf of Panama.

Gemmula benthina – Dall, 1918: 318 (lapsus calami); Powell, 1964: 279 (lapsus calami).

Pleurotoma truncata Schepman, 1913 View in CoL . 2798 m, Banda Sea   GoogleMaps , Indonesia, 6°24′S, 124°39′E.

Bathybermudia carynae Haas, 1949 . 3109 m, off Bermuda, 32°08.2′N, 64°33′W.

Remarks: This species was not present in the sampling of Puillandre et al. (2012), but was included in the phylogeny of Puillandre et al. (2011) under the name Ptychosyrinx carynae .

Owing to the frequent loss of the shell apex, there are few available protoconchs for this species. Only the eroded protoconch of the type specimen of Bathybermudia carynae could be measured, with PD = 1.3 mm and PL > 1.6 mm, consisting of more than three whorls .

The radula is of medium length, ~ 2.6 mm (0.44 of AL), composed of 74 transverse rows of teeth. Marginal teeth are 118–128 µm long (mean 120 µm, N = 5), duplex. The anterior (inner) one-third of the tooth length is solid, narrow in dorsal view, pointed; in the posterior two-thirds, major and accessory limbs are broadly bifurcating, and the accessory limb has a clear constriction at about half the tooth length, slightly shorter than the major limb. The central formation has a distinct narrow carinated cusp and lateral inconspicuous flaps with indistinct lateral and anterior margins ( Fig. 7B, C).

Although this species can be distinguished from its congeners by the frequent loss of the first whorls, and from its sister species Cryptogemma praesignis by the slightly larger diameter of the shell, the bathymetry is its most distinct characteristic. Cryptogemma praesignis is found between ~300 and ~ 1400 m depth, whereas C. phymatias is the only Turridae , to our knowledge, to be found exclusively below ~ 1400 m deep. Moreover, it is the only Turridae so far, and possibly the first reported benthic gastropod, to have a Pacific–Atlantic distribution ( Fig. 4; see Discussion). Most studied type specimens have eroded shells, but the variability of the last whorls, siphonal twist and aperture among them agrees with the variability in the sequenced specimens. Note that the etymology of this species combines ‘ Cryptogemma ’ (hidden gems) and ‘ phymatias ’ (one who has tubercules), resulting in a confusing combination.

List of COI diagnostic sites (position: character state): [379: T; 493: C; 622: C]. Indexing starts right next to the 3′ end of the LCO1490 primer (from 1 to 658).

Distribution: From the central Indo-Pacific (Banda Sea) to the North Atlantic Ocean ( Bermuda Island) ( Fig. 4A), from a depth of ~1400 to ~ 3000 m ( Fig. 5). This species is expected to be found in the Indian Ocean, as is the case with other Indo-Pacific species of Cryptogemma , but it has not been documented there, presumably owing to a lack of sampling at bathyal depths.