Ondina semicingulata (Dall, 1927) Dall, 1927

Pimenta, Alexandre D., Santos, Franklin N. & Cunha, Carlo M., 2018, Redescription and reassignment of Ondinasemicingulata to the Pyramidellidae, with review of the occurrence of genus Evalea in the Western Atlantic (Gastropoda), Zoosystematics and Evolution 94 (2), pp. 535-544 : 535

Ondina semicingulata (Dall, 1927) comb. n. Figures 1 a–n, 2 a–c

Acteon semicingulatus : Dall 1927: 19-20; Poirier 1954: 102; Marcus 1974: 319; Abbott 1974: 311.

Odostomia (Evalea) ryclea : Dall 1927: 85. New synonym.

Type material.

Ondina semicingulata - Syntypes: USNM 107913 [5 shells], from type locality; Odostomia (Evalea) ryclea - Holotype: USNM 108365, R/V Albatross, sta. 2415, off Georgia (30°44'N 79°26'W, 805.2 m depth) depth, on broken coral, coarse sand and broken shell bottom).

Type locality.

R/V Albatross, sta. 2668, off Fernandina, Florida [Cumberland Island, off Georgia], (30°58 ’30” N, 79°38 ’30” W, 538 m depth).

Material examined.

The syntypes and: Off Barbados: 183 m depth, USNM 87264, [1], Blake Expedition; Upper Pliocene (Lower Pinecrest) of Sarasota Co., Florida, USA: Harry Lee Private Collection [1]; Brazil: Amapá state: off Cape Orange, (4°27 ’54.0” N, 49°58 ’05.0” W, 160 m depth), MNRJ 26217, [2], R/V Sartro 25 coll., 13/x/2000; off Maracá Island, (2°21 ’00.0” N, 48°29 ’54.0” W, 72 m depth), MNRJ 27809, [2], R/V Columbus Iselin coll., 22/x/1991; Ceará state: off Camocim, (2.089S, 41.084W, 390 m depth): MNRJ 27823, [9]; MNRJ 27830, [1], R/V Natureza coll., 30/x/2001; Rio Grande do Norte state: off Touros, (4.861S, 35.134W, 384 m depth), MNRJ 27821, [7], R/V Natureza coll., 24/xi/2001; off Sibaúma, (6.234S, 34.876W, 510 m depth), MNRJ 27834, [2], R/V Natureza coll., 26/x/2001; Bahia state: off Itacaraé, (14.482S, 38.901W, 278 m depth), MNRJ 28264, [1], R/V Natureza coll., 02/vii/2001; off Salvador, (13.238S, 38.578W, 316 m depth), MNRJ 26258, [1], R/V Astro Garoupa, 25/vi/2002; Santa Catarina state: off Itajaí, (26°38 ’44.9” S, 46°51 ’54.2” W, 150 m depth), MNRJ 15318, [3], ii/2004.

Redescription.

Shell small, thin, up to 3.2 mm, width ~50% of length; oblong ovate to biconical; color translucent white; spire regularly conical, ~30° angled, ~40% of shell length. Protoconch heterostrophic, helicoidal, with about one smooth whorl, intorted, oriented ~180° to teleoconch axis, immersed into first teleoconch whorl, with no visible nucleus; width about 210 μm; transition with teleoconch weak, hardly discernible. Teleoconch up to four stepped whorls, each whorl slightly convex, last whorl somewhat globose; suture deep, forming a narrow furrow. Axial sculptured absent, except for growth lines; spiral sculpture with very narrow spiral grooves of variable distribution and number; usually restricted to the periphery, near the area of implantation of the outer lip, extending anteriorly up to about 1/3 of last whorl and on the base; young shells with three-four very thin furrows; some adult shells with up to 20 furrows covering all base surface and extending anteriorly on last whorl more than half of its length, but not reaching anterior suture; adult shells with visible furrows just above suture; spiral furrows covered by microscopic axial threads. Aperture elliptical-oblong, length about half of last whorl length, anteriorly elongated-rounded, posteriorly narrow and somewhat acute. Columellar margin slightly concave, without tooth. Outer lip thick. Umbilicus deep and wide, ranging from circular to wide chink.

Geographic distribution.

USA: Florida (type locality); Barbados (present study); Brazil: Amapá, Ceará, Rio Grande do Norte, Bahia and Santa Catarina states (present study).

Remarks.

Except for the features of soft parts, absent in the type specimens of Acteon semicingulatus , all characteristics agree with the diagnose provided by Høisæter (2014) for Ondina , including the oblong-ovate shell, oblong aperture and intorted protoconch. In comparison to the Eastern Atlantic species, which usually have more elongate shells, O. semicingulata has a wider shell, with biconical general shape. The original allocation in Acteon is rejected since Acteonids have a solid shell, with columellar tooth and rounded protoconch ( Valdés 2008).

Høisæter (2014) discussed the high variability of the surface of the shell, being smooth or with variable incised spirals. According to this author, in a single species, the spirals may cover uniformly the whole shell, they may be confined to the lower half of each teleoconch whorl or the shell may be smooth and shiny.

Ondina semicingulata (Figures 1 a–n, 2 a–c) is strongly sculptured with spiral furrows (Figure 1i) restricted to the anterior 1/3 to half of the whorls. On earlier whorls, these lines are visible only above suture (Figure 1 e–g), but on the last whorl, they are visible also below the periphery of whorl (Figure 1e), extending to the base (Figure 1g). The amount of lines on the last whorl (including the base) is variable, both ontogenetically and between shells with the same number of whorls.

Figure 1 j–n illustrates shells of O. semicingulata in a growth series. The amount of spiral lines and strength of the spiral sculpture increase from shells of younger specimens (Fig. 1 j–k) to adult ones (Fig. 1 l–n). Besides these three adult specimens, with same number of whorls, exhibit variation in the sculpture, covering almost entire last whorl of the shell in Figure 1m.

Odostomia (Evalea) ryclea with type locality off Goergia is here considered a synonymy name of Ondina semicingulata , since it has identical shell shape and protoconch. Despite the eroded shell surface of the holotype (Figure 2 a–c), the original description ( Dall 1927) states the presence of spiral lines in the teleoconch whorls.