Sibogasyrinx maximei, Kantor & Puillandre, 2021

Kantor, Yuri I. & Puillandre, Nicolas, 2021, Rare, deep-water and similar: revision of Sibogasyrinx (Conoidea: Cochlespiridae), European Journal of Taxonomy 773, pp. 19-60 : 46-48

Sibogasyrinx maximei sp. nov. (= PSH 9)

urn:lsid:zoobank.org:act:EEC38F7C-DD00-46B9-9D56-3915EB0B2CD2

Figs 8E , 10A–C

Diagnosis

Shell medium-sized, reaching 41.6 mm in length, fusiform, subsutural ramp weakly concave on early teleoconch whorls, flat on later ones. It is nearly smooth (except for axial riblets). Shoulder of teleoconch whorls with nodules, absent on last whorl. Spiral sculpture weak, of indistinct closely spaced cords on and below shoulder. Radula with central tooth and longitudinally folded marginal teeth with weakly thickened edges.

Etymology

This species is named after Maxime, the son of the second author.

Material examined

Holotype SOLOMON SEA • off Marshall Bennett I. ; 08°38′ S, 151°46′ E; depth 720 m; MADEEP, stn DW4323; MNHN-IM-2013-45883 .

Description (holotype)

MEASUREMENTS. SL 41.6 mm, AL (with canal) 23.2 mm, AL (without canal) 15.7 mm, SW 12.4 mm.

SHELL. Moderately thick, strong except for fragile and partially broken outer aperture lip, fusiform, with high, conical spire and moderately long, broad, straight siphonal canal. Protoconch small, globose, of about 1.5 strongly convex, microshagreened whorls. Protoconch/teleoconch transition marked by strongly arcuate axial rib, corresponding to shape of growth line. Protoconch diameter 1.0 mm, height 0.83 mm. Spire whorls weakly angled at shoulder, last whorl with hardly discernible shoulder. Total teleoconch whorls 8.5. Suture shallowly impressed, subsutural ramp broad, weakly concave on first four teleoconch whorls, flat on later whorls. Subsutural ramp with short, distinct, prosocline axial wrinkles, corresponding to upper parts of thickened growth lines, extending from suture to upper ⅓ of ramp, increasing in number from 20 on first whorl to 34 on penultimate and 43 on last whorl. Subsutural ramp with only traces of indistinct spiral striation. Shoulder of teleoconch whorls (except last one) with a row of distinct elongated nodules, these nearly orthocline on upper whorls and weakly opisthocline on penultimate whorl, 14–17 per whorl, reaching lower suture and intersected by spiral cords. Starting from 2 nd teleoconch whorl, spiral cords appearing on shoulder, these intersecting nodules and becoming progressively stronger, from two on 2 nd whorl to nine on penultimate one. Cords very closely spaced, separated by narrow grooves. On last whorl cords cover entire shell surface below indistinct shoulder, about 50 cords in total, of which 25 on canal. Cords weak, slightly wavy, very closely spaced just below suture and with intervals 0.5–1.0 times width of cords on shell base and canal. Shell base gradually narrowing towards moderately broad, almost straight siphonal canal. Aperture narrow, constricted posteriorly, with narrow and very thin parietal callus, outer lip partially broken, evenly convex and weakly concave at transition to canal. Anal sinus moderately deep, subsutural, broadly arcuate, confluent with large forward extension of outer lip. Shell very light yellowish, protoconch light tan. Periostracum smooth, tightly adhering.

RADULA (n = 1; MNHN-IM-2013-45883) ( Fig. 8E ). Medium-long, comprising 40 rows of teeth, 12 nascent. Radula length 1.8 mm (11.4% of AL without canal), width up to 290 μm (1.85% of AL without canal). Central tooth with basal plate, having distinct borders and long, narrow, sharp cusp, anterior margin overlapped by preceding row, posterior margin formed by two straight sections meeting at obtuse angle in midline. Marginal teeth flat when formed, becoming trough-shaped with weakly thickened edges during maturation, folded longitudinally when fully formed, with both margins overlapping at tooth tip. Resulting folded tooth moderately broad with sharply pointed tip, border between both margins present as a narrow slit at anterior edge. Tooth folding occurring within 14 th row of teeth (counting from rear).

Remarks

The species is known from the holotype alone and is very similar to Sibogasyrinx clausura sp. nov. (for comparison see remarks under the following species). In shell outline it is very similar to S. cf. pyramidalis 1 and 2, but differs in having fewer nodules on the shoulder; the holotype has 17 nodules on the penultimate whorl, whereas specimens of S. cf. pyramidalis 1 and 2 of similar size have up to 26 nodules. There are additional differences in radular morphology.

Distribution

Known only from the type locality.

Figures

Fig. 8. Radulae of species of Sibogasyrinx Powell, 1969. A–B. Sibogasyrinx sangeri Kantor, Fedosov & Puillandre, 2018, MNHN-IM-2009-16995 (shell seen on Fig. 7C). A. Part of radula with fully formed marginal teeth; white hollow arrow indicates overlapping edges of the tooth at its tip. B. Part of radula showing transition between unfolded (white arrow) and completely longitudinally folded (black arrow) marginal teeth (ae = anterior tooth edge; pe = posterior tooth edge). C. Sibogasyrinx filosa Ardovini, 2021, Solomon Islands, MNHN-IM-2009-16831 (shell seen Fig. 9E–F). D. Sibogasyrinx lolae sp. nov., MNHN-IM-2009-29311. E. Sibogasyrinx maximei sp. nov., holotype, MNHN-IM-2013-45883, anterior end of radula. F. Sibogasyrinx pagodiformis sp. nov., MNHN-IM-2009-11327.

Fig. 10. A–C. Sibogasyrinx maximei sp. nov., Solomon Sea, holotype, MNHN-IM-2013-45883, SL 41.6 mm. D–M. Sibogasyrinx clausura sp. nov. D–F. Solomon Islands, holotype, MNHN- IM-2013-48256, SL 41.4 mm. G–H. Coral Sea, Coriolis Bank, MNHN-IM-2013-48167, SL 37.9 mm. I–J. Solomon Islands, MNHN-IM-2009-16763, SL 29.6 mm. K–L. Coral Sea, Coriolis Bank, MNHN- IM-2013-48244, SL 35.6 mm. M. Coral Sea, Coriolis Bank, MNHN-IM-2013-48144, SL 31.7 mm. All shells to same scale.