Costaclis hyalina

Costaclis hyalina (Watson, 1881)

(Figure 2 A–G)

Aclis hyalina Watson, 1881a: 246–247. Watson (1886: plate 34, figure 2a–d); Lange-de-Morretes (1949: 82); Rios (1975: 62, plate 16, figure 245 [reproduced from original illustration]); Rios (1985: 52, plate 19, figure 234 [reproduced from original illustration]); Rios (1994: 106, plate 34, figure 438 [reproduced from original illustration]);

Aclis nucleata Dall, 1889b: 325–326, plate 18, figure 7. Synonymized by Bouchet & Warén (1986).

Aclis lata auct. non. Dall, 1889b: Dall (1927: 70).

Hemiaclis benedicti Bartsch, 1947: 22–23, plate 5, figure 5. Synonymized by Bouchet & Warén (1986).

Hemiaclis hyalina auct. non (Watson, 1881a): Bartsch (1947: 21, plate 6, figure 5).

Costaclis hyalina (Watson, 1881a): Bouchet & Warén (1986: 450).

Type material. Lectotype (herein designated): NHMUK 1887.2.9.1575 (Figure 2A, B); paralectotypes (herein designated): NMW 1955.158.26258 [3 dd], from type locality. Aclis nucleata Dall, 1889b: holotype USNM 126830 (Figure 2C, D); Hemiaclis benedicti Bartsch, 1947: holotype USNM 87356 (Figure 2E).

Type locality. Brazil: Off Pernambuco, Challenger stn. 122 (09°04′48″S 34°49′48″W, 640 m), coll. 10/ ix/1873.

Material examined. Type material.

Measurements. Lectotype NHMUK 1887.2.9.1575, ~12 whorls, SL= 10.4 mm; BWL= 3.8 mm; AL= 2.0 mm; SW= 3.2 mm; AW= 1.7 mm. Paralectotype NMW 1955.158.26258, 9 whorls, SL= 5.4 mm; BWL= 2.4 mm; AL= 1.5 mm; SW= 2. 0 mm; AW= 1.0 mm. Paralectotype NMW 1955.158.26258, 8 whorls, SL= 4.0 mm; BWL= 1.9 mm; AL= 1.1 mm; SW= 1.5 mm; AW= 0.8 mm

Remarks. Watson (1881a) did not fix a holotype and did not mention the number of specimens upon which the description was based. Two lots of Aclis hyalina collected from Challenger stn. 122 were found in the NHMUK and NMW, which are considered syntypes. Watson (1881a) recorded the species only from the Challenger stn. 122.

The original label of the NHMUK syntype states “f’ type” [figured type], and comparing this syntype to the illustration of Watson (1886: plate 34, figure 2a–d), it is clear that he figured and measured the shell from NHMUK 1887.2.9.1575 (Figure 2A, B). This shell is selected as the lectotype (Figure 2A, B). Barros et al. (2003) wrongly cited holotype and paratypes of “ H. hyalina ” under “BMNH [=NHMUK] 2346”. As discussed above, the material originally consisted of syntypes and the catalog number is incorrect.

The original description of the species is appropriate to the lectotype and there is no need for a redescription. We just emphasize that the species does not present spiral sculpture as described by Watson (1881). The spiral lines cited by him (“visible in a changing light”) are probably a refractive phenomenon commonly seem in eulimid shells (Warén 1983: 14).

Costaclis hyalina was formerly described in Aclis (Watson 1881a). Bartsch (1947) erected the genus Costaclis Bartsch, 1947 for species of Aclididae with well or poorly developed axial ribs, but classified A. hyalina in the genus Hemiaclis G.O. Sars, 1878. Bouchet & Warén (1986: 300) transferred the genera Costaclis and Hemiaclis to Eulimidae and proposed the combination C. hyalina, which we follow in the present study.

The lectotype of Costaclis hyalina (Figure 2A, B) presents poorly developed axial ribs, which are more evident in the incremental scars, appearing as gentle varices. The holotypes of A. nucleata (USNM 126830) (Figure 2C, D, F, G) and H. benedicti (USNM 87356) (Figure 2E), junior synonyms of C. hyalina (Bouchet & Warén 1986), present the ribs more pronounced, especially in the initial teleoconch whorls of A. nucleata (Figure 2G). We consider these small differences in the development of the sculpture as a variation or a condition of the worn status of these shells.

Bouchet & Warén (1986: 450) mentioned that Costaclis mizon (Watson, 1881) (Figure 3E), from the eastern Atlantic (Watson 1881a) and Gulf of Mexico (Rosenberg et al. 2009: 582), may be a synonym of C. hyalina. Indeed, the spire angle and width of the whorls are very similar in the lectotype of C. hyalina and in the holotype of C. mizon (NHMUK 1887.2.9.1574) (Figure 3E), however, C. mizon has a much more well-developed sculpture than any other specimen of C. hyalina from the western Atlantic. For now, we consider C. mizon as a valid species based on the teleoconch sculpture.

Costaclis hyalina was known only from the type locality for a century, until some new records in the last decades. However, subsequent records of C. hyalina in Brazil are very dubious or based on misidentifications.

Mello & Perrier (1986: 121) recorded “ Aclis hyalina ” based on material collected in the intertidal zone, thus this is possibly a misidentification. There is no illustration of the species and the material could not be traced in the LMUFRPE.

Barros et al. (2001: figure 2d) recorded “ Hemiaclis hyalina ”, but this is a misidentification and the shell figured by these authors is possibly a new species of Aclis. The shell illustrated has more convex whorls and the aperture is further expanded laterally. The record by Barros et al. (2002) presents no illustrations and could not be traced in LMUFRPE, but it seems dubious by the shallow depth of the collecting stations (around 50 m). The record of “ H. hyalina ” by Barros et al. (2003: figure 1) is also dubious, because the figured specimen is very young and does not permit a precise identification.

Thus, based on the reevaluation of previous records of C. hyalina in the literature, we consider them invalid and the species is known in Brazil by the type material only.

Geographical distribution. USA: Georgia, Florida (Dall 1927; Bartsch 1947); St. Vincent and the Grenadines: St. Vincent (Dall 1889b); Brazil: Pernambuco (Watson 1881a).

Bathymetric distribution. From 538 m to 848 m.