Strobiligera cf. compsa ( Dall, 1927 )

Fernandes, Maurício Romulo, 2024, The deep-sea species of Triphoridae (Gastropoda, Triphoroidea) from Guadeloupe, sampled by the Karubenthos 2 expedition, European Journal of Taxonomy 972, pp. 1-52 : 24-27

Strobiligera cf. compsa ( Dall, 1927)

Fig. 12

Triphora (Strobiligera) compsa Dall, 1927: 96 .

Triphora (Strobiligera) compsa – Abbott 1974: 112, fig. 1154.

Inella compsa – Rolán & Fernández-Garcés 2008: 118, fig. 17f–g.

Strobiligera compsa – Fernandes & Pimenta 2014: 169; 2019a: fig. 3r.

Type material

Lectotype

USA • sh; off Georgia; 805 m depth; USNM 333518.

Paralectotype

USA • 1 sh; same locality as for lectotype; USNM 1592924.

Material examined

GUADELOUPE (Karubenthos 2 expedition) • 1 sh; stn DW4572; MNHN • 25 sh, 3 specs stored dry; stn DW4646; MNHN • 2 specs stored in ethanol; same data as for preceding; MNHN-IM-2019-20014 .

Emended description

Shell sinistral, conical, up to 8.1 mm long (adult shells reach at least 5.8 mm in length), 2.1 mm wide, length/width ratio 3.7–4.7, apical angle of early whorls 19–24°; some shells show a distinct change in width on seventh teleoconch whorl or after (indicated by a scar), becoming broader, whereas others maintain their width; additional scars may appear in late whorls, after which teleoconch sculpture may become smooth, polished. Protoconch paucispiral, truncated, 2.5–3.0 whorls, 0.44–0.59 mm long, 0.43– 0.54 mm wide; small nucleus rises in an adapical direction and further goes abapical in an oblique descent; two smooth, wide spiral cords of equal size, situated at 34–37% and ~69% of last whorl height, in addition to a narrow subsutural cord; transition to teleoconch demarcated by a thin scar in some shells, but not discernible in others. Teleoconch with up to 12 whorls; three main spiral cords (continuous to those of protoconch), two of them (median and abapical) stronger at beginning, adapical spiral cord initially narrow but gradually strengthening along teleoconch, reaching nearly same size as other cords between sixth and ninth whorls; suture distinct, with a smooth sutural cord; 22–25 nearly orthocline axial ribs on eighth teleoconch whorl; moderately large, nearly rounded nodules; wide, smooth subperipheral cord, two smooth basal cords (adapical one prominent, abapical narrow); two supranumerical cords appear in some shells, one between adapical and median cords, another between median and abapical cords; oval, broad aperture, 0.87–1.19 mm long, 0.62–0.88 mm wide, length/width ratio 1.0–1.4; open, very short anterior canal, 0.17–0.38 mm long, 0.26–0.31 mm wide, length/width ratio 0.6–1.4; posterior sinus very small. Shell white. Operculum elliptical, moderately thin but rigid, semi-transparent, up to 3.5 distinct whorls, nucleus slightly eccentric, dislocated 34–43% from center towards margin.

Remarks

The lectotype of S. compsa (figured in Rolán & Fernández-Garcés 2008; Fernandes & Pimenta 2019a) is very similar to some shells from Guadeloupe ( Fig. 12A ), but the absence of protoconch and base in the type material precluded comparisons. The lectotype (12 mm long and 3.3 mm wide for 13 teleoconch whorls) is slightly larger than shells from Guadeloupe (up to 8.1 mm long, 2.1 mm wide for 12 teleoconch whorls). The geographic distance of 2400 km between the type locality and Guadeloupe is also large for a non-planktotrophic species (assuming that the population from Georgia, USA has the same development mode). Therefore the present identification is tentative.

According to Fernandes & Pimenta (2019a), records of S. compsa from Brazil are erroneous. The records from intertidal sites in Venezuela ( Nava & Severeyn 2010; Severeyn et al. 2017) are also incorrect, requiring images for further identification.

Another very similar species to S. cf. compsa from Guadeloupe is Strobiligera torticula ( Dall, 1881) , from Yucatán Strait and the Straits of Florida ( Rolán & Fernández-Garcés 2008; Fernandes & Pimenta 2015b). These two species are particularly similar with respect to their shells, which show a distinct change in their width after the seventh teleoconch whorl ( Fig. 12C, E–F ). However, the shell of S. torticula is larger (up to 25 mm long for 17.5 teleoconch whorls – Rolán & Fernández-Garcés 2008) than that of S. cf. compsa (up to 8.1 mm long for 12 teleoconch whorls), and the protoconch of S. torticula is multispiral, typical of planktotrophic development ( Fernandes & Pimenta 2015b), instead of the paucispiral protoconch, typical of non-planktotrophic development in S. cf. compsa ( Fig. 12I, M ).

The most similar species to S. cf. compsa in Guadeloupe is S. variabilis sp. nov., but S. cf. compsa has much more convex whorls, a wider body whorl and base, more widely spaced basal cords (not too close to the subperipheral cord, as in S. variabilis ), and the spiral cords of the protoconch never show the ‘crispy’ condition (with small nodules) observed in some shells of S. variabilis .

Geographic distribution

USA: Georgia ( Dall 1927); Guadeloupe (this study).

Bathymetric distribution

Empty shells previously known from 805 m ( Dall 1927). This study: 250–399 m (empty shells), 250– 254 m (live specimens).

Figures

Fig. 12. Strobiligera cf. compsa (Dall, 1927). A–B, J–M. MNHN-IM-2019-20014, stn DW4646 (K–L from shell A; J, M from shell B), 7.6 mm, 6.9 mm. C–I. MNHN, stn DW4646 (G–I from shell C), 6.2 mm, 7.8 mm, 8.1 mm, 5.8 mm. Scale bars: A–F, L = 1 mm; G–I = 500 µm; J–K, M = 200 µm.