Sinetectula cinis Fraussen & Vermeij 2021, gen. et comb. nov.

Sinetectula cinis (Reeve, 1846) gen. et comb. nov.

Figs 3, 10D–E

Buccinum cinis Reeve, 1846: [1], plate 11 no. 84 (see Fig. 10D) (type (s) not traced).

Caducifer? thaleia Pilsbry & Lowe, 1932: 67, pl. 6 fig. 6 (see Fig. 10E) (one syntype in ANSP 81972).

Pisania cinis – Tryon 1881: 147, pl. 71 fig. 204.

Caducifer (Monostiolum) cinis – Keen 1971: 557–558, no. 1100.

Type localities

Buccinum cinis: Galápagos Archipelago, “Gallapagos [sic] Islands (under stones)”.

Caducifer? thaleia: Costa Rica, Cocos Island.

Material examined

Syntype

COSTA RICA • 1 sh, type of C. thaleia; Cocos Island; 5°32′ N, 87°04′ W; R.E. Snodgrass leg.; Jul. 1899; ANSP 81972.

Other material

COSTA RICA • 1 lv; Cocos Island, Dos Amigos; 2010; KF 1013 (see Fig. 3E–H) • 6 additional lots (not specified); Cocos Island; SBMNH.

GALAPAGOS • 1 sh; Santa Cruz Island, Academy Bay; AMNH 110439 • 1 sh; Santa Cruz Island, Academy Bay, under rocks in tide pool; USNM 812823 • 1 sh; north of Santa Cruz Island, under rocks at low tide; USNM 824680 • 1 sh; Hood Island; AMNH 89659 • 1 sh; Rabida Island; AMNH 111853 • 2 sh; San Cristóbal Island; SBMNH 24676 • 1 sh; Isla Baltra, at low tide under rocks; USNM678930 • 1lv; Isla Fernandina, under rocks;depth 10–15m;NMR94140 • 1sh;“ Galápagos Islands ”; USNM 171968 • 1 sh; “ Galápagos Islands ”; LACM 120909 • 1 lv; Isla Baltra, between rocks and rubble; depth 3–4 m; KF 2123 (see Fig. 3A–D) • 2 lv; Santa Cruz Island, trawled; depth 30 m; KF 7466.

Distribution

Sinetectula cinis gen. et comb. nov. is restricted to the central eastern Pacific. We studied specimens from Costa Rica and Galápagos. López-Pérez (2013) recorded the species from Mexico. We have not studied the material from Mexico preserved in SBMNH or the material from Colombia preserved in UV.

Remarks

Sinetectula cinis gen. et comb. nov. merits special attention because of the presence of a distinct labral tooth. The tooth, first noted by Vermeij (2001: 464, 475, 497), is the eighth (counting from the suture) of 13 outer-lip serrations (without counting along the siphonal canal) formed as an enlarged and protruding space between external spiral cords. A single specimen (KF 2123) has an additional weak tooth formed by the seventh outer-lip serration (see Fig. 3D).

Only Sinetectula nigricostata gen. et comb. nov. has, occasionally, a similar labral tooth, but no comparable labral tooth is found among members of such related genera as Bailya M. Smith, 1944, Caducifer, Clivipollia, Dianthiphos Watters, 2009, Jeannea Iredale, 1912, Monostiolum, Parabailya Watters & Finlay, 1989, Parviphos or Speccapollia Fraussen & Stahlschmidt, 2016.

At a maximum length of 34.5 mm (Simon Aiken: pers. com. 2020), S. cinis gen. et comb. nov. is also the largest member of this genus. This exceptional size could be related to the high planktonic productivity of the waters around the Galápagos Islands. Other species of the genus are smaller and they usually live in reef environments where planktonic productivity tends to be low.

We follow Keen (1958: 398, 1971: 557–558) and consider Caducifer? thaleia to be a subjective junior synonym of S. cinis gen. et comb. nov. The type specimen (ANSP 81972), from Cocos Island, has a damaged outer lip and therefore does not show a labral tooth; but specimens from Cocos Island (SBMNH) with an intact outer lip do express a labral tooth. Specimens from Costa Rica are not obviously different from typical S. cinis gen. et comb. nov. from the Galápagos Islands, apart from the usually somewhat slenderer shape.

Sinetectula shepstonensis gen. et comb. nov., a species from eastern Africa with an almost identical sculpture, differs from S. cinis gen. et comb. nov. in its more equally sculptured outer lip without labral denticle, the slightly finer spiral sculpture with fine secondary spiral cords, the more convex whorls and the weakly constricted base resulting in a slightly narrower siphonal canal.

Sinetectula nigricostata gen. et comb. nov. is the second member of the genus that has an apparent labral denticle. It differs from S. cinis gen. et comb. nov. in its convex whorls, the broader shape with a shorter spire, the finer spiral sculpture, the stronger axial ribs that are lower in number, the weak or absent incremental lamellae, the constricted base with longer siphonal canal, the pattern consisting of fine spiral lines and the smaller adult size.