Fusceulima watsoni Souza & Pimenta & Barros 2021, sp. nov.

Fusceulima watsoni sp. nov.

urn:lsid:zoobank.org:act: 2C702913-5836-4DC0-ABA1-1B4ED3E518B0

(Figure 10 A–I)

Type material. Holotype NMW 1955.158.11589 (Figure 10A); Paratypes: MNRJ 23054 † [1 dd] (Figure 10C, D), MNRJ 35264 [9 dd] (Figure 10 E–I), Off Rio Grande do Norte, REVIZEE Nordeste (04°51′40″S 35°08′01″W, 384 m), coll. RV Natureza, 24/xi/2001; NMW 1955.158.27216 [1 dd] (Figure 10B), from the type locality.

Type locality. Brazil: Pernambuco, Challenger stn. 122.

Etymology. After Rev. Robert Boog Watson (1823–1910), who described several eulimids from deep waters off Northeast Brazil collected during the Challenger Expedition.

Description (Holotype). Shell subconical, apex broad, obtuse, reaching 2.8 mm long, 1.0 mm wide. Protoconch-teleoconch transition not visible. Whole shell with about 5.5 whorls, slightly sinuous outline, convexity confined to the lower region of each whorl; suture shallow, slightly impressed, sloping; surface glossy and smooth; incremental scar weak, only one appearing on the body whorl. Last whorl about 65% of the shell length; base elongated, slightly rounded outline. Aperture high, pear shaped, acute posteriorly and rounded anteriorly; outer lip thin, slightly sinuous, almost orthocline, projecting gently and gradually from suture to a point below the middle of its height and retracting gently and gradually in the distal region; inner lip sinuous, sloping and well demarcated. Not umbilicate. Shell vitreous or whitish.

Measurements. Holotype NMW 1955.158.11589, 5.5 whorls, SL= 2.8 mm; BWL= 1.8 mm; AL= 1.2 mm; SW= 1.0 mm; AW= 0.6 mm. Paratype MNRJ 23054, 6 whorls, SL= 3.0 mm; BWL= 1.8 mm; AL= 1.2 mm; SW= 1.0 mm; AW= 0.6 mm.

Remarks. The paratypes MNRJ 23054 (Figure 10C, D) and MNRJ 35264 (Figure 10 E–I) were destroyed during the fire in the MNRJ, but the types in the NMW are safely preserved.

The shell of this species is extremely smooth, except for the small wrinkles in the suture of the protoconch (Figure 10J). The protoconch-teleoconch transition is not clearly visible, but by the sculpture and shape of the larval shell this species possibly has non-planktotrophic development, like other species of Fusceulima (Souza & Pimenta 2014). A single incremental scar is present on the body whorl.

Fusceulima watsoni sp. nov. resembles F. toffee Souza & Pimenta, 2014, from the continental shelf of Southeast Brazil, by the similar shape of the shell and of the aperture, but has less convex teleoconch whorls and is whitish or completely vitreous (Figure 10 A–D) while F. toffee has a dark brown color (Souza & Pimenta 2014: figure 46–47).

Fusceulima watsoni sp. nov. can be distinguished from F. victorhensenae Hoffman & Freiwald, 2017, from western Morocco, by being larger (paratype MNRJ 23054, 6 whorls, SL= 3.0 mm vs. holotype of F. victorhensenae, 6 whorls, SL= 1.8 mm) (Hoffman & Freiwald 2017), with less convex teleoconch whorls and a less protruding outer lip.

Fusceulima watsoni sp. nov. differs from other Atlantic congeners mainly by the more conical shell (Figure 10 A–E) and by the higher aperture (Figure 10F). Most of deep-sea Fusceulima from the Atlantic have a more cylindrical shell and a shorter aperture, for example: F. coralensis Hoffmann & Freiwald, 2017, from western Morocco; F. minuta (Jeffreys, 1884) (Souza & Pimenta 2014: figs. 29–31), from the Northeast Atlantic; F. sordida (Watson, 1897) (Figure 10K), from the Madeira archipelago; and F. thalassae Bouchet & Warén, 1986 (Figure 10L), from the Northeast Atlantic.

Geographical distribution. Brazil: Rio Grande do Norte and Pernambuco (present study).

Bathymetric distribution. From 384 m to 640 m.