Eulimacrostoma phorcys Souza & Pimenta & Barros 2021, sp. nov.

Eulimacrostoma phorcys sp. nov.

urn:lsid:zoobank.org:act: 128029A4-10BA-401F-B39D-9AA3ECEDFC0D

(Figure 9 A–I)

Melanella hians auct. non Watson, 1883: Lima et al. (2005: 2, figure 1a–d).

Type material. Holotype: MNRJ 23191 † (Figure 9A, B). Paratypes: from type locality, MNRJ 35191 † [5 dd] (Figure 9 C–I); Brazil: off Sergipe, REVIZEE Nordeste (10°41′24ʺS 36°18′42ʺW, 365 m), 28/x/2000, MNRJ 35220 † [3 dd].

Type locality. Brazil, Off Rio Grande do Norte, REVIZEE Nordeste (04°51′S 35°06′W, 375 m), coll. RV Natureza, 24/xi/2001.

Etymology. A sea god from Greek mythology, Phorcys (Latin spelling) is associated with the hidden dangers of the sea. Epithet as a noun in apposition.

Description (Holotype). Shell conical, apex obtuse, reaching about 7.6 mm long, 1.8 mm wide. Larval shell vitreous, with about 1.75 whorls, 300 µm wide, 375 µm in height, smooth, transition to teleoconch marked by a subtle incremental scar. Teleoconch with 9.0 whorls, sinuous outline, convexity more attenuated on the lower region of each whorl; suture deep, well impressed, sloping; subsutural zone about 1/5 of the height of the whorl; surface glossy, presenting micro sculpture of opisthocline axial lines; incremental scars well developed, appearing at irregular intervals. Last whorl about 45% of the shell length; base rounded. Aperture high, wide, pear shaped, slightly expanded laterally, acute posteriorly, rounded and spread anteriorly; outer lip thin, very sinuous, opisthocline, retracted near the suture, after strongly projecting, and retracted in the distal region, maximum projection at the middle of the outer lip height; inner lip thin, sinuous, sloping. Not umbilicate. Teleoconch vitreous, with a wide yellowish spiral band at the lower region of each whorl.

Measurements. Holotype MNRJ 23191†, 11 whorls, SL= 7.6 mm; BWL= 3.4 mm; AL= 2.2 mm; SW= 1.8 mm; AW= 1.0 mm. Paratype MNRJ 35191†, 11 whorls, SL= 7.6 mm; BWL= 3.6 mm; AL= 2.5 mm; SW= 2.2 mm; AW= 1.3 mm. Paratype MNRJ 35191†, ~10 whorls, SL= 6.9 mm; BWL= 3.4 mm; AL= 2.3 mm; SW= 1.9 mm; AW= 1.2 mm. Paratype MNRJ 35191†, 9 whorls, SL= 5.8 mm; BWL= 3.0 mm; AL= 2.1 mm; SW= 1.7 mm; AW= 1.1 mm.

Remarks. All types of the present species were destroyed; however, it has consistent shell features that allow the description as a new species, and the figures provided here are sufficient for its recognition.

The present species fits the recently described genus Eulimacrostoma, because it has a subcylindrical protoconch (Figure 9H), microsculpture of very thin axial lines on the teleoconch (Figure 9E), an aperture gaping anteriorly (Figure 9F) and a strongly protruding outer lip (Figure 9G) (Souza & Pimenta 2019a).

The record of Melanella hians (Watson, 1883) from the continental slope of Pernambuco, Brazil, by Lima et al. (2005) is actually a misidentification of Eulimacrostoma phorcys sp. nov. The material studied by these authors could not be found in the LMUFRPE, but the figured specimen (Lima et al. 2005: figure 1a–d) is clearly conspecific with E. phorcys sp. nov. Thus, M. hians is known only from the the type locality in Culebra Islands, Puerto Rico (Challenger stn. 24).

Eulimacrostoma phorcys sp. nov. can be distinguished from M. hians by the narrower teleoconch whorls, which results in a smaller spire angle, and by features of the aperture, which is more rounded and gaping in the anterior region but less expanded laterally.

Eulimacrostoma phorcys sp. nov. closely resembles E. microsculpturatum Souza & Pimenta, 2019, from the Caribbean and Florida, by the general shape of the shell, color pattern of the teleoconch and the presence of several incremental scars. However, E. phorcys sp. nov. has the first protoconch whorl strongly inflated, with a wider diameter (250 μm vs. 200 μm in E. microsculpturatum) (Figure 9I) and the same maximum diameter (300 μm) despite reaching a smaller number of whorls (2.0 vs. 2.5). Additionally, the protoconch of E. phorcys sp. nov. has no trace of a brownish spiral band while E. microsculpturatum has one (Souza & Pimenta 2019a). Eulimacrostoma phorcys sp. nov. also differs by the larger size; the holotype has about 11 whorls and reaches 7.6 mm long while the paratypes USNM 433081 and USNM 1273894 of E. microsculpturatum with the same number of whorls are 6.5 and 6.6 mm long (Souza & Pimenta 2019a), respectively. No sexual dimorphism is known in the genus.

Eulimacrostoma phorcys sp. nov. can be distinguished from E. chascanon (Watson, 1883), known only from the type locality (same as Melanella hians), mainly by the wider apex and anterior region of the aperture, and by the larger size (holotype of E. phorcys, 11 whorls, SL= 7.6 mm vs. syntype NHMUK 1887.2.9.1587, 12–13 whorls, SL= 4.5 mm).

Eulimacrostoma phorcys sp. nov. can be distinguished from E. patula (Dall & Simpson, 1901), from the Caribbean and northern Brazil, by the absence of an umbilical chink and by the more rounded base in younger and mature specimens.

Eulimacrostoma phorcys sp. nov. can be distinguished from E. lutescens (Simone, 2002), from Southeast Brazil, by being proportionally smaller in length (holotype, 11 whorls, SL= 7.6 mm vs. holotype of E. lutescens, SL = 8.9 mm) and by the shorter and narrower aperture (AL= 2.2 mm, AW= 1.0 mm, AW/AL= 0.4 vs. AL= 3.1, AW= 1.6, AW/AL= 0.5, holotypes of both species).

Geographical distribution. Brazil: Rio Grande do Norte (present study), Pernambuco (Lima et al. 2005) and Sergipe (present study).

Bathymetric distribution. From 365 m to 690 m (Lima et al. 2005; present study).