Inella

Fernandes, Maurício Romulo & Pimenta, Alexandre Dias, 2019, Taxonomic review of Inella and Strobiligera (Gastropoda: Triphoridae) from Brazil, Zootaxa 4613 (1), pp. 1-52 : 24

“ Inella ” leucocephala sp. nov.

Figure 12

urn:lsid:zoobank.org:act:4D9E7E84-49AD-4793-B8D9-849D0FEB39B9

Type material. Holotype: MNRJ 18637 . Paratypes: Brazil: Espírito Santo state : MNRJ 33816 , 18 º 46ʹ 48ʺ S, 38º 31ʹ 24ʺ W, 65 m, 20/iv/1985 [1] ; MNRJ 32658 [1] , MNRJ 32661 [1], 20º 14ʹ S, 40º 12ʹ W, vi/2008 ; MORG 40404 , REVIZEE-Central C1-VV22 [1] ; MNRJ 34031 , Ilha Escalvada, Guarapari , 2012 [1] ; MNRJ 31080 , 20 º 47ʹ S, 40º 34ʹ W, iii/2010 [1]; IBUFRJ 19687, Piúma, 1993 [7]. Rio de Janeiro state : MNRJ 18303 [1] , MNRJ 18711 [1], HAB 13-H2 ; MNRJ 18642 , HAB 16-H2 [1]; IBUFRJ 19583, REVIZEE-Central C1-D3 [5] .

Other material examined. Brazil: Espírito Santo state: MNRJ 32295 , 19 º 24ʹ 17ʺ S, 39º 15ʹ 33ʺ W, 45 m [1]; IBUFRJ 19615, REVIZEE-Central C1-VV38 [1]; MNRJ 32651 [1], MNRJ 32652 [2], MNRJ 32655 [1], 20º 14ʹ S, 40º 12ʹ W, vi/2008 ; MNRJ 33797 , REVIZEE-Central C1-VV21 [1]; MNRJ 31033 [1], MNRJ 31044 [2], MNRJ 31063 [1], 20º 47ʹ S, 40º 34ʹ W, iii/2010 .

Type locality. HAB 16-H3, 21º 43ʹ 06ʺ S, 40º 11ʹ 37ʺ W, 71 m, Rio de Janeiro state, Brazil .

Etymology. leukos, Gr. = white; cephalo, derived from the Gr. kephale = head. It refers to the color of the apex of these shells.

Diagnosis. Protoconch with two spiral cords, the adapical one disappearing one to two whorls after its emergence; median spiral cord emerges in the second or third whorl of teleoconch; protoconch and first whorl of teleoconch white, remainder whorls brown.

Description. Shell sinistral, elongated, conical, rectilinear profile, reaching 11.23 mm in length, 2.69 mm in width, length/width ratio 3.4 to 3.9. Protoconch slightly globose, subcylindrical, 0.45–0.67 mm in length, 0.44–0.54 mm in width in its last whorl; 2.75 to 3.75 convex whorls, weak distinction between protoconch and teleoconch; initial whorl dome-shaped but slightly pointed, covered by small rounded granules; remaining whorls initially with two spiral cords, situated at 32–37% and 58–74% of whorl height, the adapical one disappearing one to two whorls after its emergence, the abapical one readily strengthening and assuming a keeled shape on the last whorl; small or almost indistinct axial wrinkles more evident above the adapical cord, being orthocline to much oblique. Teleoconch with up to 14 whorls; two spiral cords (adapical and abapical) in the beginning, the abapical one continuous with that of the protoconch; median spiral cord emerges in the second or third whorl, reaching the same size of other cords after 1.5 to 2 whorls; on the body whorl, distance between spiral cords is 0.9 to 1.8 times the width of cords; 18 to 21 orthocline to slightly opisthocline axial ribs; rounded (especially in the adapical cord) to elliptical (median and abapical cords) nodules of a medium to small size, becoming less pronounced on late whorls of large shells; distinct and well-developed suture, with a small sutural cord; narrow and weakly nodulose to wavy subperipheral cord, two slightly wavy to smooth basal cords; two very fine threads may appear behind the peristome in some shells, one above, the other below the median spiral cord; ovate aperture, 0.69–0.86 mm long, 0.52–0.71 mm wide, length/width ratio 1.2–1.3; anterior canal curved almost downwards, moderately long and open or partly closed by the projection of the outer lip, 0.28–0.50 mm long, 0.24–0.30 mm wide, length/width ratio 1.0–1.7; posterior canal a small notch, 0.14–0.17 mm long, not detached from the aperture. Protoconch and first whorl of teleoconch white, remainder whorls light brown to brown; coloration usually faint in worn shells.

Remarks: There is intraspecific variation in “ Inella ” leucocephala sp. nov. regarding the protoconch ( Fig. 12 J–K), as the variable number of protoconch whorls (2.75 to 3.75) is associated with great differences in its size (0.45–0.67 mm in length, 0.44–0.54 mm in width) and in the persistence of the adapical spiral cord (for one to two whorls). The coloration pattern of “ Inella ” leucocephala sp. nov. ( Fig. 12 A–D) is similar to that of the Caribbean species Isotriphora peetersae Moolenbeek & Faber, 1989 .

A juvenile of “ Inella ” leucocephala sp. nov. ( Fig. 12E ) was sampled from Bahia state (MORG 26919, Ilha Guarita, Abrolhos, 5 m). Owing to this unusual shallow bathymetric record and the early developmental stage of the shell, Bahia was not included in the geographical distribution list of this species, requiring more specimens to confirm this northward range.

Geographical distribution. Brazil: Espírito Santo and Rio de Janeiro .

Bathymetric distribution. 33–80 m.

Figures

FIGURE 12. “Inella” leucocephala sp. nov. A. MNRJ 18637, holotype, 11.23 mm. B. MNRJ 18711, paratype, 5.46 mm. C. MORG 40404, paratype, 7.30 mm. D. MNRJ 31080, paratype, 4.33 mm. E. MORG 26919, 1.55 mm. F. MNRJ 18303, paratype, 5.33 mm. G, I: same shell as F. H, K: MNRJ 32658, shell not illustrated. J, L: same shell as C. Scale bars: A–F, 1 mm; G–I, 500 µm; J–L, 100 µm.