Cyclocardia velutina ( Smith, 1881 )

Güller, Marina & Zelaya, Diego G., 2013, The Families Carditidae and Condylocardiidae in the Magellan and Perú – Chile provinces (Bivalvia: Carditoidea), Zootaxa 3682 (2), pp. 201-239 : 209-211

Cyclocardia velutina ( Smith, 1881)

Figs. 4 A– O, 9C, Appendix 4

Cardita (Actinobolus) velutinus Smith, 1881: 42 , pl. 5, fig. 8.

Cardita velutina Smith—Rochebrune & Mabille, 1889 : H111; Stempell, 1899: 231. Cardita magellanica Philippi, 1898: 89 .

Venericardia (Cyclocardia) velutina Smith, 1881 — Dall, 1903: 708.

Venericardia (Cyclocardia) velutina Smith—Dall, 1908: 412 ; Lamy, 1922: 342. Venericardia velutina Smith—Dall, 1909: 261 .

Cardita velutina— Kaspar, 1913: 548.

Cyclocardia velutina Smith, 1881 — Soot-Ryen, 1959: 39.

Cyclocardia velutina ( Smith, 1881) — Dell, 1964: 191; Osorio & Reid, 2004: fig. 3f. Venericardia velutina (Smith) —Ageitos de Castellanos, 1970: 233 (in part). Cyclocardia velutinus [sic] [recte velutina ] Smith, 1881 — Osorio & Reid, 2004: 83; Cárdenas et al., 2008: 230, figs. 7.88–90.

Type localities: Port Rosario, 2–30 fathoms [4–55 m], Wolsey Anchorage, 17 fathoms [31 m] [ Cardita (Actinobolus) velutinus ]; “Sinu del Almirantazgo, maribus magellanicis” [= Seno Almirantazgo] ( Cardita magellanica ).

Material examined: 2 syntypes ( NHMUK 1879.10.15.145-146) and 2 possible syntypes from “Patagonia” ( NHMUK 1869.7.28.13) of Cardita (Actinobolus) velutinus , and 42 lots (Appendix 4, Table 1 ).

Other published records: Beagle Channel ( Rochebrune & Mabille, 1889); Chile ( Dall, 1908; Kaspar, 1913; Soot-Ryen, 1959; Osorio & Reid, 2004; Cárdenas et al., 2008) (Appendix 4, Table 2 ).

Known distribution: Seno Reloncaví [41°S], Chile to Malvinas / Falkland Islands [51°S], and extending northwards in the Southwest Atlantic to off Buenos Aires Province [37°S]. Living specimens: 15– 252 m.

Description: Shell large (maximum observed L = 19.4 mm), subcircular to ovate in larger specimens (H/L = 0.99 ± 0.04, n = 5), subequilateral, inflated (W/H = 0.76 ± 0.07, n = 5), solid ( Figs. 4 A–K). Anterior end slightly produced, lower than the posterior end. Antero-dorsal margin concave to nearly straight, forming a well marked angle at the junction with anterior margin. Anterior, ventral and posterior margins regularly curved. Postero-dorsal margin with a straight slope, longer than antero-dorsal margin ( Figs. 4 A–H, J, K). Lunule short, wide, and deep.

Escutcheon narrow, elongated ( Fig. 4 I). Beaks inflated, subcentral to anteriorly displaced, directed forward ( Figs. 4 A–K). Prodissoconch small (about 230 µm in length) ( Fig. 4 L). Shell surface sculptured with 15–20 strong, rounded radial ribs, bearing conspicuous tubercles; interspaces as wide as or wider than radial ribs, with fine commarginal lamellae ( Figs. 4 A, B, D, E, O). Periostracum thick, brown, forming short hair-like projections, and commarginal folds in interspaces ( Figs. 4 A–F, O). Inner margin strongly crenulated, coincident with outer shell sculpture ( Figs. 4 G, H, J, K). Pallial line continuous ( Figs. 4 G, J).

Hinge plate solid, oblique, anterior and posterior halves nearly equal in height ( Figs. 4 M, N). Right valve ( Fig. 4 N): anterior cardinal tooth (CA3) hooked, dorsally fused with shell margin; anterior part (CA3a) short, extremely thin, ventrally directed; posterior part (CA3b) high, large, with wide triangular base. Posterior cardinal tooth (CP5b) long, narrow, slightly arcuate, parallel to nymph, with distal cusp. Anterior lateral tooth (LAI) minute, knob-like. Posterior lateral tooth (LPI) short, massive, close to dorsal margin. Left valve ( Fig. 4 M): two solid, divergent cardinal teeth, dorsally fused with shell margin. Anterior cardinal (CA2a) high, ventrally directed, with subcentral cusp, one third the size of the posterior one (CP4b). Posterior cardinal elongated, slightly arcuate, gradually widening distally. Anterior lateral (LAII) small but distinct. Posterior lateral (LPII) small, narrow. Ligament external, located on a nymph which extends for about two thirds the length of posterior part of dorsal margin ( Figs. 4 I, M, N).

Anatomy (Fig. 9C): Mantle margin with a large inhalant-pedal aperture, extending for about 5/6 mantle margin length, separated from a small posterior exhalant opening by a short suture. Transverse section of anterior adductor muscle large, reniform; transverse section of posterior muscle ovate, two thirds the size of the anterior one. Inner and outer demibranchs posteriorly fused with each other and to mantle margin. Outer demibranch one half the size of inner one, showing up to 100 filaments (in the larger studied specimen); ascending and descending lamellae equally developed. Inner demibranch with 110 filaments (in the larger studied specimen); ascending lamella as high as descending lamella. Labial palps with 5–6 strong sorting ridges.

Remarks: Cyclocardia velutina differs from C. compressa in being more homogeneously rounded, more inflated and solid, in having narrower and higher ribs with nodules, and a pilose periostracum. Cyclocardia velutina also has a deeper lunule and escutcheon. The larger specimens of C. velutina resemble C. thouarsii and C. spurca in general shell outline (see remarks of those species).

The original description of Cardita magellanica reveals that this name is a synonym of Cyclocardia velutina . The species was never illustrated , and the types were not found.

Ageitos de Castellanos (1970) identified two lots from off Buenos Aires as Cyclocardia velutina (under Venericardia ). However, only the lot MACN-In 25183 corresponds to this species whereas lot MACN-In 24191 actually corresponds to Cyclocardia moniliata Dall, 1903 , a species here reported for the first time from Argentine waters.

Figures

FIGURE 4. Cyclocardia velutina. A, D, G, J: Syntype of Cardita (Actinobolus) velutinus, Port Rosario, 4 – 55 m (NHMUK 1879.10.15.145); B, E, H, K: Puerto Parry, 35 m (MACN-In 39060); C, F, M, N: Bahía Lapataia, 120 – 138 m (MLP 12212); I, L: Isla Gable, 66 – 68 m (MLP 12207); O: Isla Lilihuapi, 80 – 94 m (MACN-In 39062). A – F: Outer views; A – C: Right valve; D – F: Left valve; G, H, J, K: Inner views; G, H: Left valve; J, K: Right valve; I: Dorsal view; L: Prodissoconch (arrow shows P- 1 / P- 2 boundary); M, N: Detail of hinge plate; M: Left valve; N: Right valve; O: Shell sculpture and periostracal projections. Scale bars: A – H, J, K = 1 cm; I, M, N = 2 mm; L = 100 µm; O = 200 µm.