Setia ermelindoi Avila & Cordeiro

Cordeiro, Ricardo & Avila, Sergio P., 2015, New species of Rissoidae (Mollusca, Gastropoda) from the Archipelago of the Azores (northeast Atlantic) with an updated regional checklist for the family, ZooKeys 480, pp. 1-19 : 3-5

Taxon classification Animalia Littorinimorpha Rissoidae

Setia ermelindoi Avila & Cordeiro sp. n. Figure 2

Setia cf. lacourti (Verduin, 1984): Segers (2002: 89).

Type material.

Holotype, DBUA 1058 (sh., 1.07 × 0.76 mm), São Miguel Island (Caloura, 5-15 m depth, 21/05/1999); paratype 1, DBUA 1079 (spc., 1.08 × 0.80 mm), Pico Island (Lajes do Pico, 1-2 m depth, 24/06/1991); paratype 2, DBUA 1080 (spc., 0.74 × 0.59 mm); paratype 3, DBUA 1081 (spc., 0.92 × 0.76 mm), Pico Island (Lajes do Pico, intertidal, 24/06/1991); paratype 4, DBUA 1082 (spc., 0.94 × 0.70 mm), Flores Island (Santa Cruz, intertidal, 09/07/1989); paratype 5, DBUA 1083 (spc., 0.79 × 0.63 mm); paratype 6, DBUA 1084 (spc., 0.94 × 0.66 mm); paratype 7, DBUA 1085 (spc., 0.78 × 0.62 mm), Flores Island (Santa Cruz, intertidal, 08/08/2010).

Type locality.

Caloura, São Miguel Island, Azores.

Additional material examined.

Pico Island: DBUA 467 (Lajes do Pico, intertidal, 1 sh., 07/1989). São Miguel Island: DBUA 137 ( Ilhéu de Vila Franca do Campo, intertidal, 2 spc., 07/1988); DBUA 689 ( São Vicente, 22 m depth, 1 sh., 15/07/1996); DBUA 899 (Faial da Terra, 8.3 m depth, 2 spc., 10/10/1996); DBUA 957 (Pesqueiro, 5.6 m depth, 1 spc., 19/07/1997).

Etymology.

Named after Ermelindo Ávila, a writer and historian from Pico Island.

Description.

Shell minute, translucent, globose, up to 1.1 × 0.8 mm (Fig. 2A). Protoconch paucispiral, whorls 1.25, diameter 225-235 µm, smooth, with no visible sculpture, except for a few faintly developed axial growth lines, separated from the teleoconch by a clearly visible line (Fig. 1G and H). Teleoconch with 1.75 to 2 inflated, rounded, strongly convex whorls sculptured by faint axial lines (no spiral sculpture present); whorls with regular contour and conspicuous increase in width (Fig. 2 B–E). Spire short. Suture deep, constricted (Fig. 2 B–E). Last whorl very large, globose, 75-80% of shell length (Fig. 2 B–E). Base large, rounded. Aperture oval and oblique with faint posterior angulation (Fig. 2 B–E). Parietal region moderately thickened, rather straight to very slightly convex (Fig. 2 B–E). Outer lip thin, smooth inner surface (Fig. 2 B–D). Inner lip thin, slightly reflected over umbilicus (Fig. 2 B–E). Umbilicus a moderately enlarged fissure (Fig. 2 B–E). One axial threads always present and running abapically nearby the umbilicus (Fig. 2D). Animal black (Fig. 2A). Foot whitish. Operculum simple, thin, nucleus eccentric, translucent (Fig. 2E and F).

Habitat.

On rocky shores covered by algae, from the intertidal down to 25 m depth.

Geographical distribution.

Flores, Pico and São Miguel Islands. Probably endemic to the Azores.

Remarks.

This species differs from most of the known Setia species by its globose shell. Setia lacourti (Verduin, 1984) and Setia valvatoides (Milaschewitsch, 1909) also have globose shells, but Setia ermelindoi sp. n. is easily separated from these species by the aperture shape, which is oval in Setia ermelindoi sp. n. and rounded in Setia lacourti and Setia valvatoides . Setia ermelindoi sp. n. is also distinguished by the axial thread running abapically near the umbilicus. The shell shape of Setia ermelindoi sp. n. resembles that of some Rissoella species (e.g., Rissoella contrerasi Rolán & Hernández, 2004 and Rissoella inflata (Monterosato, 1880)). However, the animal lacks the typical two pairs of head tentacles found in all Rissoella ; instead, it has only one pair typical of Rissoidae . Moreover, Setia ermelindoi sp. n. does not have the pigmented hypobranchial gland (observable through the transparent shell) of several Rissoella (a species-diagnostic character, cf. Rolán and Hernández 2003; e.g., Rissoella contrerasi , Rissoella luteonigra Rolán & Rubio, 2001, Rissoella trigoi Rolán & Hernández, 2004, Rissoella caribaea Rehder, 1943, and Rissoella ornata Simone, 1995).