Aforia obesa, Pastorino, Guido & Sánchez, Noelia, 2016

Pastorino, Guido & Sánchez, Noelia, 2016, Southwestern Atlantic species of conoidean gastropods of the genus Aforia Dall, 1889, Zootaxa 4109 (4), pp. 458-470 : 463-464

Aforia obesa new species.

Figures 4 A–M; figures 5 A–E; figures 6 A–E

Description. Shell large, biconic, fusiform, young shells translucent, adults chalky white in color, up to 34 mm height; protoconch paucispiral, globose, about two whorls (~ 1.45 mm width x 2.08 mm height), irregular oblique spiral wrinkles visible; Anal sinus appears on second whorl of larval shell; transition to teleoconch gradual; teleoconch comprising 5 whorls; anal sinus at the upper third of the spire whorls and above the periphery on the last whorl, with the deepest part forming a slightly raised selenizone on the whorls, which otherwise are gently rounded and lack a keel; suture moderately deep; axial ornamentation of irregularly spaced growth lines all along shell; spiral ornamentation of fine, gently, undulating spiral threads increasing in number, 5 in the first whorl, 8 on second and third whorl, 17 on the fourth and up to 90 on the last whorl below selenizone; above selenizone, 7 in the first whorl, 8 on second and third to 11 on the fourth and fifth whorls; anterior siphonal canal narrow and very long; aperture elliptical.

Operculum oval (juveniles) or oval elongated (adults), with subterminal nucleus, brownish, translucent.

Radula of type 3 “ Turridae ” according to Kantor & Taylor (2000), short, rachidian unicuspid, with curved base, faint secondary denticles at both sides of central cusp, each one showing continuity towards the base, marginal teeth duplex with a flat major element; accessory limb robust, thick, base attached to radular membrane and major element. Penis long and broad, flat with large conical terminal papilla surrounded by a thin collar. Eyes large as in A. goniodes . Table 3 summarizes shell measurements of the new species.

Type material. Holotype, MACN-In 40475, ( Figure 4 A–C), Paratypes, MACN-In 40476, 40477, 40478, 40479; MLP-Ma 14176; CNP-Inv 2048.

Type locality. 38°01.631'S, 54°30.275'W in 997 m depth, collected on May 26 2013, St. 41 “ Talud Continental ” expedition of R/V “PUERTO DESEADO”.

Etymology. obesa : fat in Latin, in relation to the thick profile in the last whorl of the shell.

Material examined. All specimens collected on “ Talud Continental ” expedition of R/V “PUERTO DESEADO”: MACN-In 40476, St. 8, 37°57.857´S, 54°57.406´W, in 647 m, 5 SH, 1 SP; MACN-In 40477, St. 10, 37°59.706´S, 54°41.854´W in 852 m, 1 SH, 1 SP; MACN-In 40479, St. 14, 38°0.984´S, 54°30.326´W in 1006 m, 10 SH, 6 SP; MACN-In 40480, St. 43, 37º53.837´S, 54º30.458´W, in 998 m depth, 3 specimens; MACN-In 40478, St. 44, 37°53.557'S, 54°42.941'W in 780 m, 2 SH, 1 SP; MACN-In 40481, St. 59, 37°49.688'S, 54°5.236'W in 1398 m, 2 SH; MLP-Ma 14176, St. 41, 38°01.631'S, 54°30.275'W in 997 m, 3 SH, 4 SP; CNP-Inv 2048, St. 44, 37º53.557´S, 54º42.941´W, in 780 m depth, 2 SP.

Distribution. Only known from localities around the Mar del Plata Submarine Canyon in 647 to 1,398 m depth.

Remarks. This species can be distinguished from all other Atlantic representatives of Aforia by the lack of a distinct keel, having instead a kind of raised selenizone near the upper one-third of the spire whorls. The spiral ornamentation consists of wavy threads and no microscopic granules were present as in A. goniodes , the only sympatric species. The profile of the shell of A. obesa n. sp. looks similar to A. lepta ( Watson, 1881) from New Zealand and A. goodei Dall, 1890 from Chiloe Is., Chile. McLean (1971) considered all deep-water species from the Eastern Pacific as a synonym of A. goodei . Both the latter species are blind (as well as A. persimilis Dall ) according to Sysoev and Kantor (1987), a character truly different from the new species here described. In addition, the rachidian tooth has weak denticles at both sides of the unique central cusp, in A. obesa n. sp. a feature, which in fact, separates it from every known species of Aforia . Also, the size of the accessory limb of the marginal tooth is thicker than in A. goniodes .

Antarctic species. A. magnifica and A. multispiralis , both common Antarctic species, were studied for comparative purposes only.

Figures

FIGURE 4. Aforia obesa new species. A – C, Holotype, MACN-In 40475, St. 41; D – F, paratype, MACN-In 40476, St. 8; G, Operculum, interior and exterior view, scale bar = 5 mm; H – J, paratype, MACN-In 40477, St. 10; K – M, paratype, MACN-In 40478, St. 44.

Tables

TABLE 3. Measurements of Aforia obesa n. sp. in mm. AL: aperture length; AW: aperture width; SL: shell length; SPL: spire length; SW: shell width. * Holotype, ** Paratype.

Specimen	1	2	3	4	5(Fig.4 A–C)*	6	7	8
St.	8	8	14	14	41	41	43	43
SL (mm)	36	30	37	39	40	35	35	37
SW (mm)	11	11	12	13	13	12	11	11
AL (with canal) (mm)	21	20	23	23	24	21	22	23
AL (without canal) (mm)	13	12	14	16	16	14	18	13
AW (mm)	9	5	7	6	6	6	6	6
SPL (mm)	15	10	14	16	16	14	13	14
SW/SL (%)	30.6	36.7	32.4	33.3	32.5	34.3	31.4	29.7

continued.