Strobiligera unicornium ( Simone, 2006 ) Fernandes & Pimenta, 2019

Fernandes, Maurício Romulo & Pimenta, Alexandre Dias, 2019, Taxonomic review of Inella and Strobiligera (Gastropoda: Triphoridae) from Brazil, Zootaxa 4613 (1), pp. 1-52 : 33-35

Strobiligera unicornium ( Simone, 2006) comb. nov. Figures 17–19

Inella unicornium Simone, 2006: 6 , fig. 1–2, 5–7, partim.

Type material. Holotype: MZSP 78886 ( Fig. 17 A–B). Paratypes: MZSP 78890 ( Fig. 17 C–F), type locality [4].

Type locality. 02º 14ʹ 25ʺ S, 38º 22ʹ 50ʺ W, 240–260 m, Canopus Bank, off Ceará state, Brazil.

Material examined. The type material and: Brazil: off Maranhão state: USNM 810450, 0º 18ʹ N, 44º 16ʹ 48ʺ W, 274 m, Oregon R/V coll., 09/iii/1963 [2]. Off Ceará state: MNRJ 30402 [5], MZSP 66560 [1], MZSP 93891 [4], MZSP 94251 [1], type locality, P.M.S. Costa & J. Coltro coll., xi/2005; MZSP 53729 [1], MZSP 90270 [2], MZSP 70277 [5], MZSP 70291 [2], MZSP 133330 [8], type locality, J. Coltro & C.M. Cunha coll., viii/2005.

Description. See Simone (2006) for the description of the teleoconch. The protoconch is herein described, based on lots MZSP 53729, MZSP 66560, MZSP 70277 and MZSP 90270, all from the type locality: protoconch globose, much to little inflated, 0.69–0.76 mm in length, 0.48–0.63 mm in width of its first whorl, 0.52–0.62 mm in width of its last whorl; 2.75 to 3.0 whorls, unclear distinction between protoconch and teleoconch, transition defined by a fine, sinuous/opisthocline axial mark; initial 1.5 or 1.75 whorls dome-shaped, broad, white, mostly smooth and translucent; remaining 1.25 whorls with a distinct or faint light brown color, with two main spiral cords, the abapical one initially slightly more prominent, in addition to two minute subsutural cords and one small cord situated right above the suture; two main spiral cords respectively situated at 40–46% and 67–75% of last whorl height; axial sculpture absent except by fine axial marks present above the adapical spiral cord.

Remarks. This is one of the largest triphorids of the world, reaching 49.7 mm in shell length ( Simone 2006). The main problem related to the original description of S. unicornium is that its single paratype lot is a mix of three species ( Fig. 17 ), one of them being Strobiligera gaesona , which is recorded in Brazil in the present study (see below). The protoconch illustrated by Simone (2006) as being S. unicornium actually belongs to S. gaesona , and the real protoconch of S. unicornium is herein described and illustrated ( Fig. 19 ), fitting the globose paucispiral protoconch of Strobiligera and rendering the new generic allocation. Indeed, worn shells of S. unicornium and S. gaesona may be mistaken, but they differ on the broader profile of S. unicornium , its expanded outer lip, the reduced adapical spiral cord through most whorls of the teleoconch, a stronger spiral sculpture on the teleoconch (also developing small elliptical granules, absent in S. gaesona ), and protoconch with a faint or distinct light brown color (but entirely white in S. gaesona ) and discrete axial marks above its adapical spiral cord.

Simone (2006) differentiated S. unicornium from Inella colon ( Dall, 1881) ( Fig. 3W ), from Cuba and Florida ( U.S.A.), by having a larger shell size, proportionally longer whorls, taller spiral cords and a projected outer lip. Two shells identified by Rolán & Fernández-Garcés (2008: figs. 16E–F) as I. colon , although they noted differences compared to the type material of this species, are very similar to S. unicornium ; one shell is from Yucatan ( Mexico), the other from Florida ( U.S.A.). These shells seem to present a much reduced adapical spiral cord on the teleoconch, which is somewhat similar to the holotype of S. unicornium , but not to the majority of shells of this species (with a gradually developing adapical spiral cord). In addition, their bathymetric range (236–366 m) is more similar to that of S. unicornium (240–274 m) than to the type material of I. colon (823–1834 m); further comparison is required to evaluate if S. unicornium has a wider geographical range.

Despite the broken apex, the two shells of USNM 810450 ( Fig. 18 G–H) are herein referred to S. unicornium owing to a very large size, similar teleoconch sculpture (although the adapical spiral cord is slightly more developed), identical bathymetric records and close geographical distribution, thus extending the known range of this species to Maranhão state.

Geographical distribution. Brazil: off Maranhão (this study), off Ceará (type locality) .

Bathymetric distribution. 240 m (type locality) to 274 m (this study).

Figures

FIGURE 3. Type material of some species of Inella and Strobiligera. A–B. “Inella” intermedia (Dall, 1881), lectotype MCZ 7386 (A), non-type MCZ 7385 (B). C–D. “Inella” triserialis (Dall, 1881), paralectotypes MCZ 7384 (C) and MCZ 7382 (D). E–F. “Inella” faberi Rolán & Fernández-Garcés, 2008, holotype FLMNH 291343 (E), paratype FLMNH 419388 (F). G. “Inella” differens Rolán & Lee, 2008, holotype FLMNH 419184. H–I. “Inella” undebermuda Rolán & Lee, 2008, holotype FLMNH 419181 (H), paratype USNM 1112657 (I). J. “Inella” longissima (Dall, 1881), lectotype MCZ 7381. K–L. “Inella” harryleei Rolán & Fernández-Garcés, 2008, holotype FLMNH 419182 (K), paratype FLMNH 158178 (L). M. Strobiligera sentoma (Dall, 1927), lectotype USNM 108072. N. “Inella” pseudolongissima Rolán & Fernández-Garcés, 2008, paratype FLMNH 171183. O–P. Inella pseudotorticula Rolán & Lee, 2008, holotype FLMNH 419191 (O), paratype USNM 1112658 (P). Q. Strobiligera pompona (Dall, 1927), lectotype USNM 108339. R. Strobiligera compsa (Dall, 1927), lectotype USNM 333518. S–T. Strobiligera gaesona (Dall, 1927), lectotype and paralectotype USNM 108341. U–V. Strobiligera dinea (Dall, 1927), lectotype and paralectotype USNM 333517. W. Inella colon (Dall, 1881), paralectotype MCZ 7387. X. Strobiligera enopla (Dall, 1927), lectotype USNM 108074.Y. Inella apexbilirata Rolán & Fernández-Garcés, 2008, holotypeANSP 367841, credits of image to Paul Callomon. Scale bars: A, H–R, 5 mm; B–G, S–Y, 1 mm.

FIGURE 17. Strobiligera unicornium (Simone, 2006) comb. nov., type material. A–B. MZSP 78886, holotype (credits of im- ages to Patricia Oristânio). C–F. MZSP 78890, paratypes: C–D, S. unicornium; E, Strobiligera gaesona; F, the newtoniellid Trituba anubis Fernandes, Garofalo & Pimenta, 2015. Scale bars: A–D, F, 5 mm; E, 1 mm.

FIGURE 18. Strobiligera unicornium (Simone, 2006) comb. nov., non-type material. A. MZSP 66560, 18.31 mm. B. MZSP 70277, 9.65 mm. C. MZSP 90270, 6.25 mm. D. MZSP 53729, 5.69 mm. E. MNRJ 30402, 14.29 mm. F. MNRJ 30402, 42.31 mm. G. USNM 810450, 14.38 mm. H. USNM 810450, 35.98 mm. I–J: same shell as F. K: same shell as B. Scale bars: A, E–H, 5 mm; B–D, I–J, 1 mm; K, 500 µm.

FIGURE 19. Strobiligera unicornium (Simone, 2006) comb. nov., non-type material, protoconch. A. MZSP 53729. B. MZSP 66560. C. MZSP 90270. D. MZSP 70277. Scale bars: 200 µm.