Glaciotomella investigator, Criscione & Hallan & Puillandre & Fedosov, 2021

Criscione, Francesco, Hallan, Anders, Puillandre, Nicolas & Fedosov, Alexander, 2021, Where the snails have no name: a molecular phylogeny of Raphitomidae (Neogastropoda: Conoidea) uncovers vast unexplored diversity in the deep seas of temperate southern and eastern Australia, Zoological Journal of the Linnean Society 191, pp. 961-1000 : 985

GLACIOTOMELLA INVESTIGATOR SP. NOV.

( FIG. 3G)

Z o o B a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: 0B100DF6-9DEB-402B-A382-2964754D285B.

Holotype: Australia, New South Wales, Hunter CMR, 2595 m, IN2017_ V03 _070, (–32.575, 153.162), AMS C.571621.

Distribution: Known only from the type locality.

Etymology: In reference to the Australian Government’s RV Investigator, on which the expedition was conducted that allowed for this species (and many other species described herein) to be collected. It is a noun in apposition.

Description

Shell ( Fig. 3G) (SL = 20.8, SW = 10) with cyrthoconoid spire, relatively thin-walled, chalky, semitranslucent to opaque. Protoconch largely eroded. Teleoconch of five whitish whorls with slightly concave subsutural ramp, evenly and broadly convex below. Suture deep. Subsutural ramp sculpture of fine, regularly set axial riblets. Teleoconch sculpture below subsutural ramp of orthocline axial ribs, extending from subsutural ramp to suture, prominent on early teleoconch whorls, progressively weakening toward last whorl (about 18 on penultimate whorl,> 20 on last whorl); numerous weak, densely set, collabral growth lines between axial ribs; spiral sculpture of regularly spaced cords with finer cordlets in their interspaces, more differentiable on early teleoconch whorls, resulting in distinctly cancellate early- to mid-teleoconch whorls, and with a finer meshwork of axial and spiral elements on last adult whorl. Last adult whorl broadly convex below subsutural ramp, abruptly constricted to long siphonal canal. Boundary between last whorl and siphonal canal on left side (in apertural view) deeply concave, with siphonal canal distinctly convex. Aperture broadly pyriform, about half of shell length; outer lip thin; inner lip with thin glossy whitish callus. Columella straight in apertural view, distinctly convex in lateral view. Anal sinus moderately deep, J-shaped.

Mantle of single studied specimen stained with crimson, originating from distinct, well-developed rectal gland (although this staining is certainly a postmortem feature, it may be useful to differentiate the species from conchologically similar species in other lineages). Head with small cephalic tentacles situated on either side of rhynchostome, with extremely small eyes situated at their outer base. Rhynchostome and rhynchostomal sphincter extremely large; rhynchocoel short, with proboscis occupying most of its length. Proboscis with strongly folded walls; venom gland long, convoluted; muscular bulb large.

Radula of hypodermic teeth attaining 310 µm in length, straight, cylindrical. No distinct barb or blade.

Remarks

This new taxon can be differentiated from other raphitomids by the following combination of characters: a broadly fusiform shell, with strongly convex whorl profile, cancellate sculpture on early- to mid-teleoconch whorls and a long, straight columella with a curved siphonal canal in lateral view ( Fig. 3G); an extremely large rhynchostome and long, straight and cylindrical hypodermic teeth with no distinct barb or blade.

Glaciotomella investigator is similar to Pleurotomella (specifically, compared here to type species P. packardii Verrill, 1872 , and not to Pleurotomella in the broad sense), in that both taxa possess a shell with prominent sculpture, strongly convex whorls with an impressed suture and a long siphonal canal. However, Gla. investigator differs from the latter in having a distinctly broader, more convex and less shouldered whorl profile, and a comparatively straight columella (which in P. packardii has a prominent left-turning curve toward the anterior of the siphonal canal). Furthermore, our molecular results suggest that Glaciotomella and Pleurotomella are in fact not closely related within Raphitomidae ( Fig. 2). The radula of this species is not figured due to poor preservation state.