Epitonium striatellum ( Nyst, 1871 )

Zelaya, Diego G. & Güller, Marina, 2017, Undercover speciation of wentletraps (Caenogastropoda: Epitoniidae) in the Southwestern Atlantic, Zootaxa 4286 (1), pp. 41-69 : 49-50

Epitonium striatellum ( Nyst, 1871)

( Figure 5 )

Scalaria tenuistriata d’Orbigny, 1839: 390 , pl. 54, figs. 4–6

Scala striatella Nyst, 1871: 134 –135 (nomen novum pro Scalaria tenuistriata d’Orbigny, 1839 non Bronn, 1831) Epitonium (Asperiscala) tenuistriatum: Clench & Turner, 1952: 299 –300, pl. 138; Rios, 1994: 98, pl. 32, fig. 397 Epitonium tenuistriatum: Castellanos, 1970: 63 , pl. 4, fig. 8; Scarabino, 1977: 183, pl. 2, fig. 9

Type locality. Bahía Blanca [38°42’S 62°10’W, Buenos Aires Province, Argentina].

Type material. Lectotype (NHMUK 1854.12.4.359/1) and one paralectotype (NHMUK 1854.12.4.359/2) [not examined].

Material examined. Uruguay: Rocha: [33°54’00’’S 53°31’00’’W], La Coronilla (MACN-In 19214: 2 sh.); [34°23’S 53°47’W], Cabo Polonio ( USNM 359204 : 1 sh); [34°39’0’’S 54°10’0’’W], La Paloma (MACN-In 29687: 13 sh.; MACN-In 28767: 3 sh.); [34°39’36’’S 54°09’21’’W], Cabo Santa María , Rocha (MACN-In 15305: 1 sh.) . Argentina: Buenos Aires Province : 38°25’18.50’’S 56°30’37.07’’W, off Mar del Plata (MACN-In 10740: 1 sh.; MACN-In 11995: 1 sh.); [38°53’13’’S 62°05’52’’W], Base Naval Puerto Belgrano, Punta Alta (MACN-In 6620- 23: 1 sh.; MACN-In 11211: 2 sh.); [39°42’S 62°07’W], mouth of Río Colorado (MLP-Ma 1375: 9 sh.) ; 40°18’29.79’’S 62°14’15.66’’W, Bahía San Blas (MACN-In 20266: 2 sh.) . Río Negro Province: [41°00’S 64°07’W], Aguada de los Loros, San Antonio Este (MACN-In 13339-1: 3 sh.; MACN-In 13340: + 100 sh.); [40°49’S 64°54’W], Punta Villarino, San Antonio Este (MACN-In 13365: 3 sh.) ; 40°29’35.2’’S 65°31’44.7’’W, Las Grutas, 6 m (MACN-In 40376: 1 sh.); 40°45’18.7’’S 64°56’31.8’’W, La Mar Grande, intertidal (MACN-In 40377: 8 sh.); 40°54’00.0’’S 65°06’43.1’’W, 6 m (MACN-In 40378: 1 sh.); 40°54’08.3’’S 65°06’28.0’’W, 9 m (MACN-In 40379: 1 sh.).

Known distribution. Rio de Janeiro (22°54’S), Brazil ( Rios 1994) to Golfo San Matías (40°54’S) , Río Negro Province, Argentina. Bathymetric range of living specimens unknown; shells found from the intertidal to 9 m.

Description. Shell large (maximum L observed = 23.9 mm, apex missing; to 28.5 mm according to Clench & Turner (1952)), elongate, thin, white, translucent ( Fig. 5 A–C, E, F). Protoconch and first whorls of teleoconch very eroded in all available specimens ( Fig. 5 D). Teleoconch with up to 8 whorls, slightly convex in outline; suture deep, partially covered by axial sculpture ( Fig. 5 A–C, E, F, H); last whorl evenly curved at the base. Aperture ovate; peristome with a small basal expansion. Outer margin slightly thickened. Fasciole small. Umbilicus absent ( Fig. 5 A–C, E, F).

Teleoconch densely sculptured with axial and spiral elements, which form a cancellate pattern ( Fig. 5 A–C, E, F, H, I). Axial ribs prosocline, extremely low, recurved, giving the appearance of thin, rounded cords, formed by fusion of several layers, obliquely aligned between adjoining whorls ( Fig. 5 G–I). Number of ribs increasing in successive whorls: from 36–40 in the first whorl to 52–58 in the last whorl of larger studied specimens. Ribs evenly curved along the whorl, well-entering into the suture, fused at their bases with the ribs of adjacent whorl ( Fig. 5 H); ribs on the last whorl extending to the umbilical area. Interspaces between ribs with numerous, thick spiral threads, as wide as axial elements in the first whorl, slightly narrower than axial sculpture in subsequent whorls ( Fig. 5 H, I). Among spiral elements it is possible to recognize primary and secondary threads, which produce rectangular interspaces in their intersection with axial sculpture ( Fig. 5 H, I). Spiral sculpture not crossing over axial sculpture.

Operculum, jaw and radula: Unknown.

Remarks. Although Nyst (1871) noted the homonymy of Scalaria tenuistriata d’Orbigny, 1839 and Scalaria tenuistriata Bronn, 1831 , and proposed Epitonium striatellum (formerly under Scala ) as a replacement name for the first, subsequent literature (e.g., Clench & Turner 1952; Castellanos 1970; Scarabino 1977; Rios 1994) retained the usage of d’Orbigny’s name.

Lima et al. (2012) provided a list of the Epitonium species present in the Atlantic coast of South America. In their list, the authors omitted both E. tenuistriatum and E. striatellum , but listed Epitonium striatissimum (Monterosato, 1878) as being present in Argentine waters. That species is distributed in the Mediterranean, Madeira, and SE United States, from North Carolina to Florida ( Bouchet & Warén 1986), with no documented records in Patagonia thus far known.

Figures

FIGURE 5. Epitonium striatellum (Nyst, 1871), shell. A. Original illustration of Scalaria tenuistriata (d’Orbigny, 1842: pl. 54, fig. 6). B, D – I. Specimens from La Mar Grande (MACN-In 40377). C. Specimen from 40 ° 54 ' 00.0 '' S 65 ° 06 ' 43.1 '' W (MACN-In 40378). H. Detail of fourth and fifth whorls. I. Detail of teleoconch sculpture at last whorl. Scale bars: B, E, F = 10 mm; C = 1 mm; D = 500 µm; E = 2 mm; G = 5 mm; H = 500 µm; I = 200 µm.