Inella

Fernandes, Maurício Romulo & Pimenta, Alexandre Dias, 2019, Taxonomic review of Inella and Strobiligera (Gastropoda: Triphoridae) from Brazil, Zootaxa 4613 (1), pp. 1-52 : 16-18

“ Inella ” sp. 2

Figure 8 A–J

Material examined. Brazil: Bahia state: MZSP 133326 , Parcel Paredes, Alcobaça , 2–3 m, P. J. Souza & E.P. Gonçalves coll., 15/i/1970 [1]. Rio de Janeiro state: MNRJ 18414 , HAB 16-H3 [1]; MNRJ 18297 , HAB 11-C3 [1]; IBUFRJ 19557, REVIZEE-Central C1-D3 [1]; IBUFRJ 11698, 22º 20ʹ S, 40º 32ʺ W, iv/1998 [1]; MNRJ 29509 , 22 º 40ʹ 35ʺ S, 41º 43ʹ 21ʺ W, 47 m [1]; MNRJ 32624 [1], MNRJ 32644 [2], 23º 04ʹ 14ʺ S, 40º 59ʹ 31ʺ W, 100 m ; MNRJ 18961 [1], MORG 52216 [1], 23º 04ʹ 14ʺ S, 40º 59ʹ 31ʺ W, 100 m, 17/xii/2004 ; MNRJ 31117 , 23 º 04ʹ 14ʺ S, 40º 59ʹ 31» W, 100 m, iii/2005 [1]; MNRJ 26606 , 23 º 04ʹ 14ʺ S, 40º 59ʹ 31ʺ W, 100 m, vii/2005 [1]; MNRJ 33592 , 23 º 05ʹ S, 40º 58ʹ W, 100 m [1]; MNRJ 32054 , 23 º 06ʹ 00ʺ S, 41º 06ʹ 00ʺ W, 89 m, x/2008 [1]; MNRJ 32068 , 23 º 09ʹ 00ʺ S, 41º 06ʹ 00ʺ W, 99 m, x/2008 [1]; MNRJ 32046 , 23 º 15ʹ 00ʺ S, 41º 06ʹ 00ʺ W, 112 m, x/2008 [1]. São Paulo state: MNRJ 32918 , 25 º 13ʹ 06ʺ S, 44º 59ʹ 31ʺ W, 160 m, viii/2008 [1].

Description. Shell sinistral, elongated, conical, nearly rectilinear profile, reaching 7.79 mm in length, 1.85 mm in width, ratio length/width 4.0 to 4.2. Protoconch subcylindrical, 0.85–1.08 mm in length, 0.64–0.72 mm in width of its last whorl; 4.25 to 4.75 convex protoconch whorls, weak distinction between protoconch and teleoconch; initial whorl dome-shaped, slightly globose in some cases, smooth; remaining whorls with two spiral cords, situated at 33% and 63% of last whorl height, the abapical one slightly more prominent especially at the end of protoconch, as the adapical one vanishes before the transition to the teleoconch; a subsutural small cord is also apparent on the last whorl; very small axial wrinkles above the adapical cord, being nearly orthocline to oblique. Teleoconch with up to 11 whorls; two spiral cords (adapical and abapical) in the beginning, the abapical one continuous with that of the protoconch; median spiral cord emerges narrowly at the very end of the fourth to the beginning of the sixth whorl, reaching nearly the same size as the abapical cord (the adapical one is more prominent on late whorls) after 3.5 to five whorls; on the body whorl, distance between spiral cords is 1.1 times the width of cords; 17 to 20 opisthocline axial ribs; rounded (especially in the adapical cord) to nearly elliptical (median and abapical cords) nodules of a medium size; distinct and well-developed suture, with a small sutural cord; weakly nodulose to slightly wavy subperipheral cord, two to three slightly wavy to smooth basal cords; no supranumerical cords are present, but in one shell there are two very fine threads behind the peristome; ovate aperture, 0.90–1.12 mm long, 0.87–0.89 mm wide, ratio length/width 1.0–1.1; anterior canal curved almost downwards, medium to moderately large, mainly closed, 0.62–0.78 mm long, 0.27–0.29 mm wide, ratio length/width 2.3 to 2.7; posterior canal as a wide sinus, 0.10–0.20 mm long, not detached from the aperture. Light brown to cream shell, with the base slightly darker.

Remarks. The single remarkable difference between “ Inella ” sp. 2 and shells of “ I ”. faberi from Brazil is related to the size of protoconch, as it varies from 0.85–1.08 mm in length and 0.64–0.72 mm in width (4.25 to 4.75 whorls) in “ Inella ” sp. 2, but from 0.55–0.79 mm in length and 0.51–0.59 mm in width (3 to 3.5 whorls) in “ I ”. faberi . This could represent the existence of very similar sympatric species or a single species with a considerable variation in protoconch size, as it occurs with other taxa in the present study. However, no shell was observed to possess an intermediate number of protoconch whorls (3.5 to 4.25 whorls) in the material examined.

The single shell, immature and worn, sampled from Bahia ( Fig. 8C ) cannot be confidently regarded as indicative that “ Inella ” sp. 2 truly occurs north of Campos Basin. It is probably a subfossil/fossil form, and its shallow bathymetric record is also doubtful.

A large shell from Espírito Santo state (MNRJ 30892, Fig. 8 K–L), 8.30 mm in length and 2.20 mm in width, has the adapical spiral cord of protoconch disappearing much before the transition to the teleoconch, the median spiral cord of teleoconch emerging yet at the end of the second whorl ( Fig. 8L ), and the three spiral cords of similar strength. Because of the similarity of its protoconch with “ Inella ” sp. 2 and the lack of more available material, this shell is herein illustrated without being designated as a new morphospecies.

Geographical distribution. Brazil: Rio de Janeiro and São Paulo, immature/worn shell northern up to Bahia.

Bathymetric distribution. 47–160 m. The record of 2–3 m from Bahia must be disregarded, owing to the immature/worn condition of the material .

Figures

FIGURE 8. A–J. “Inella” sp. 2. A. MNRJ 32644, 6.98 mm. B. MNRJ 33592, 6.15 mm. C. MZSP 133326, 2.85 mm. D–I: same shell as A. J: same shell as B. K–L. “Inella” sp., MNRJ 30892, 8.30 mm. Scale bars: A–D, K, 1 mm; E–G, L, 500 µm; H, 100 µm; I–J, 200 µm.