Pseudomohnia, Strong & Sirenko & McLean, 2021

Strong, Ellen E., Sirenko, Boris I. & McLean, James H., 2021, The only species of Mohnia Friele, 1879 (Caenogastropoda, Buccinoidea, Buccinidae) in the North Pacific represents an unrecognized new genus of Newtoniellidae (Triphoroidea), ZooKeys 1055, pp. 69-87 : 69

Genus Pseudomohnia gen. nov.

Newtoniellidae gen. nov. pro " Mohnia " Mohnia kurilana Dall, 1913: Sirenko, Kantor and Gulbin 2013: 156.

Type species.

Mohnia kurilana Dall, 1913, here designated (Fig. 1A ).

Description.

Shell dextral, thin, whitish in color, ~ 15-20 mm in adult shell length; whorls convex, suture deeply impressed, growth indeterminate. Protoconch large, multispiral, nucleus smooth, cancellate sculpture on subsequent whorls, transition to teleoconch gradual or indistinct. Teleoconch with spiral sculpture of fine cords and axial threads, often diminishing on body whorl and on base. Axis slightly gyrate, pervious; columellar plait lacking. Anterior canal short, slightly recurved. Operculum paucispiral with eccentric nucleus. Radula taenioglossate with small, concave rachidian, robust bicuspid lateral teeth, and slender marginal teeth with cylindrical shafts. Foot with deep propodial pedal gland and with metapodial pedal gland opening to deep medial cleft. Acrembolic proboscis short, salivary glands acinous, mid-esophageal gland well developed. Penis lacking. Nervous system epiathroid with long supra-esophageal connective.

Etymology.

In reference to the superficial similarity of the shell and its original placement in the genus Mohnia Friele, 1879 ( Neogastropoda , Buccinoidea ).

Distribution and ecology.

Known only from the Kuril and Aleutian Islands (Fig. 2 ) in 114-660 m, feeding on sponges.

Remarks.

The unique combination of shell and radula characters displayed by Pseudomohnia are unknown in the family and cannot be confused with any other genus. The recognition of Mohnia kurilana as representing a new genus of Newtoniellidae had already been noted by Sirenko et al. (2013) based on as yet unpublished evidence provided in the present paper.

As documented in a number of newtoniellids, the presence of a large, ribbed protoconch with a gradual or indistinct transition between protoconch and teleoconch, despite being multispiral, points to a non-planktotrophic and intra-capsular mode of larval development (e.g., Marshall 1977; Bouchet and Warén 1993; Tsuchida and Sasaki 1998; Gofas 2003; Fernandes et al. 2015).

Little is known of the anatomy of newtoniellids, but that of Pseudomohnia compares favorably with Houbrick’s (1987) description of Ataxocerithium eximium Houbrick, 1987 in the presence of a deep propodial pedal gland and a metapodial pedal gland opening to a deep medial cleft in the foot sole, a broad muscular snout, short acrembolic proboscis, well-developed mid-esophageal gland, and epiathroid nervous system with a long supra-esophageal connective.

Figures

Figure 1. Shell morphology of Pseudomohnia gen. nov. A, B Pseudomohnia kurilana (Dall, 1913) comb. nov A lectotype, USNM 205224. Kuril Islands B ZIN 57494 / 1. Kuril Islands C, D Pseudomohnia sp. LACM 1997 - 156.7 Aleutian Islands E-I Pseudomohnia rogerclarki sp. nov. Aleutian Islands E holotype, LACM 3776 F LACM 1997 - 174 G LACM 1997 - 174 H LACM 1997 - 163.21 I LACM 1997 - 165.20. Scale bar: 1 cm.

Figure 2. Distribution of Pseudomohnia gen. nov. in the North Pacific. Squares, Pseudomohnia kurilana (Dall, 1913) comb. nov.; circles, Pseudomohnia rogerclarki sp. nov.; stars, Pseudomohnia sp. Symbols with black fill are type localities. Scale in kilometers.