Strobiligera gaesona ( Dall, 1927 )

Fernandes, Maurício Romulo & Pimenta, Alexandre Dias, 2019, Taxonomic review of Inella and Strobiligera (Gastropoda: Triphoridae) from Brazil, Zootaxa 4613 (1), pp. 1-52 : 35-37

Strobiligera gaesona ( Dall, 1927)

Figures 3 S–T, 20

Triphora (Strobiligera) gaesona Dall, 1927: 95 .

Inella unicornium: Simone (2006 , fig. 3–4, partim).

Inella gaesona: Rolán & Fernández-Garcés (2008 : 128, fig. 20C).

Strobiligera gaesona: Fernandes & Pimenta (2014: 169) .

Material examined. The type material and: Brazil: off Ceará state: MNRJ 30401 [6], MZSP 70305 [6, all with dried soft parts], MZSP 78890 [4, but two shells worn/unidentifiable], MZSP 131829 [8], Canopus Bank, 02º 14ʹ 25ʺ S, 38º 22ʹ 50ʺ W, 240–260 m, P.M.S. Costa & J. Coltro coll., xi/2005; MZSP 37077 [2], MZSP 53685 [2], MZSP 53697 [2], MZSP 133332 [1], MZSP 66850 [1], MZSP 70300 [6], MZSP 133341 [4], MZSP 133331 [6], Canopus Bank, 02º 14ʹ 25ʺ S, 38º 22ʹ 50ʺ W, 240– 60 m, J. Coltro & C.M. Cunha coll., viii/2005 .

Description. Shell sinistral, elongated, conical-fusiform, rectilinear profile, reaching 28.56 mm in length, 4.03 mm in width, length/width ratio 7.5 to 7.7. Protoconch globose, much to little inflated, 0.66–0.86 mm in length, 0.41–0.68 mm in width of its first whorl, 0.45–0.61 mm in width of its last whorl; 2.75 to 3.5 slightly convex whorls (except first whorl), unclear distinction between protoconch and teleoconch, transition defined by a very fine, sinuous/opisthocline axial mark; initial whorl dome-shaped, broad, smooth; remaining whorls with two main spiral cords, situated at 45–52% and 66–76% of whorl height, with nearly the same strength or with the adapical spiral slightly more prominent, in addition to a small subsutural cord, rapidly enlarging to the end of the protoconch; axial sculpture absent. Teleoconch with up to 24 whorls; three spiral cords in the beginning, all of them continuous with those of the protoconch, the adapical one initially smallest but soon reaching the same size of others; very weak spiral sculpture, almost indistinct even in initial whorls, with only the micro spiral sculpture (composed of several threads) being evident in late whorls, but some shells have a strengthening of the spiral sculpture of median and abapical cords on late whorls; complete absence of axial sculpture over most of the shell, despite sinuous growth lines or discrete threads in some shells; absence of nodules, whorls totally flat, without any convexity; very indistinct suture, only marked by a small sutural cord; narrow, smooth subperipheral cord, two smooth basal cords; no supranumerical cords are distinguishable on the inconspicuous end of the body whorl; ovate aperture, with a moderately expanded outer lip, 1.09–1.32 mm long, 0.96–1.01 mm wide, length/width ratio 1.1–1.4; anterior canal very short, directed downwards, and totally open, 0.23–0.29 mm long, 0.36–0.43 mm wide, length/width ratio 0.6–0.8; posterior canal a very small notch, almost indistinct, 0.15–0.17 mm long. White shell, with a translucent initial protoconch whorl.

Remarks. As mentioned above, the single lot of paratypes of Strobiligera unicornium is a mix of three species, including Strobiligera gaesona ( Fig. 17E ), whose protoconch was illustrated by Simone (2006: figs. 3–4).

Shells from Brazil (Fig. 20) are remarkably similar to the lectotype of S. gaesona ( Fig. 3S ), without any clear difference, except the bathymetric range of this species is shallower in Brazil (240–260 m) than in the type locality (805 m). Some types also show a moderately strong spiral sculpture on earlier whorls ( Fig. 3T ), fading out later, which is slightly different from the very weak spiral sculpture since the beginning of the teleoconch in Brazilian shells; as mentioned above, shells of Strobiligera dinea ( Dall, 1927) may be mixed in that lot.

Several shells of S. gaesona from Brazil had drill holes indicative of predation by gastropods. Their smooth shells, without nodules, seem to be prone to suffer attacks.

Geographical distribution. U.S.A.: off Georgia (type locality); Brazil: off Ceará (this study) .

Bathymetric distribution. 240 m (this study) to 805 m (type locality).

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.