Cryptogemma praesignis (E. A. Smith, 1895)

CRYPTOGEMMA PRAESIGNIS View in CoL (SMITH, 1895)

( FIG. 8A–K)

Pleurotoma praesignis Smith, 1895. 1234 m, off Colombo, Ceylon [ Sri Lanka].

? Pleurotoma microscelida Dall, 1895 . 642 m, South of Oahu Island Albatross st. 3475, Hawaii.

Pleurotoma (Subulata) bisinuata Martens, 1901 . 1134 m, off East Africa   GoogleMaps , 1°49′N, 45°29′E.

Pleurotoma rotatilis Martens, 1902 . 1134 m, off Mogadishu   GoogleMaps , Somalia, East Africa, 1°49′N, 45°29′E.

Pleurotoma (Surcula) lobata G. B. Sowerby III, 1903 . 805 m, off Cape Natal, Durban and 567 m, off Buffalo River, East London , S. Africa. E. A. Smith, 1906.

Ptychosyrinx bisinuata japonica Okutani, 1964 . 620 m, Sea of Enshu-nada   GoogleMaps , Japan, 34°25.7′N, 137°58.5′E.

Ptychosyrinx lordhoweensis Kantor & Sysoev, 1991: 205 View in CoL , figs 1, 2. 1210 m, Lord Howe Rise   GoogleMaps , off eastern Australia, 30°24′S, 161°51′E.

Remarks: This species corresponds to PSH 11 in the study by Puillandre et al. (2012).

The protoconch exhibits a wide size range, with PD = 1.05–1.38 mm and PL = 1.4–1.93 mm, and from four to 5.2 whorls.

The radula is long, ~ 3.4 mm in length (0.44 of AL), formed of 72 transverse rows of teeth. The marginal teeth are 142–151 µm long (mean 149 µm, N = 5, or 1.9% of AL), duplex. The anterior (inner) one-third of the tooth length is solid, narrow in dorsal view, pointed; in the posterior two-thirds the major and accessory limbs are broadly bifurcating, and the accessory limb has a clear constriction and is bent at about half tooth length, 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. 7A).

This species is morphologically close to C. timorensis , although it differs from that species in its generally smaller size (~ 15–35 mm SL), in having a narrower last whorl and in the presence of a tertiary apertural notch in mature females. Cryptogemma praesignis also differs from C. timorensis in having a much longer radula (0.44 vs. 0.2 of AL) and relatively longer marginal teeth (1.9% of AL vs. 1.35%). Anatomical examination of Australian material (AMS C.571714 and AMS C.571704) shows that mature males (SL 29.4 and 34.9 mm, respectively) may possess extremely large and muscular penis, with a width almost equal to the width of the animal itself and with a large, long, lateral appendage situated distally. The penial tip is rather blunt, with the opening situated distally. A third, smaller Australian specimen (AMS C.571757; SL 25.7 mm) did not possess a well-developed papilla, suggesting that such a feature might develop with increasing maturity and therefore not be present in subadults. Furthermore, the shells of AMS C.571714 and AMS C.571704 did not possess a tertiary apertural notch. The observation of AMS C.571714 and AMS C.571704 supplements the findings of Kantor & Sysoev (1991) that the mature females of this species develop a tertiary apertural notch. The authors hypothesized that this structure was possibly connected with the process of fertilization. Such a feature has also been observed in C. aethiopica specimens ( Fig. 9G, I), but not in other Cryptogemma species.

The general morphology and, more specifically, the presence of a tertiary apertural notch in Pleurotoma bisinuata and Ptychosryinx bisinuata japonica supports the synonymization of these names with C. praesignis . Given that the holotype of P. bisinuata japonica is a comparatively large specimen (39 mm), the result of the LDA and the leave-one-out cross-validation procedure attributed it to C.timorensis . Possibly for the same reason, the holotype of P. praesignis (42 mm) also fell into the C. timorensis range. The result of the LDA and the leave-one-out cross-validation procedure when considering only shape predicted the two holotypes as C. praesignis (see Supporting Information, Fig. S3), thus justifying the attribution of P. praesignis to this molecular species. The sequencing of a paratype of Ptychosyrinx lordhoweensis confirmed its conspecificity with C. praesignis . Pleurotoma lobata , although conchologically similar to P. bisinuata , has never been synonymized based on the reportedly different morphology of the radula: the absence of a central tooth (= central formation as understood herein) in the specimens of P.lobata examined by Barnard (1958), contrasting with the large unicuspid rectangular-based central tooth described in P. bisinuata by Thiele (1929: 359). Powell (1964) suggested that Thiele could have mixed his radula preparations, but in light of the types of radulae of Cryptogemma ( Fig. 8), all composed of a unicuspid central formation, it is more likely either that it was Barnard who mixed up the radula preparation or that the specimens examined by Barnard are not Cryptogemma specimens. The holotype of Pleurotoma rotatilis is almost identical conchologically to a sequenced juvenile from the East African coast (MNHN-IM-2013-62900; Fig. 8J). Some doubts remain regarding the status of Pleurotoma microscelida , but the size and overall last whorl morphology of the type specimen show a stronger resemblance to C. praesignis than to any other Cryptogemma species.

List of COI diagnostic sites (position: character state): [232: A; 319: T; 407: C; 409: T].

Distribution: This species is known to occur from the western Indian Ocean to the eastern Pacific Ocean ( Fig. 4B), from a depth of ~300 to ~ 1400 m ( Fig. 5).