Cyrtopleura (Scobinopholas) lanceolata (d'Orbigny, 1841)

Delfino, Marina & Signorelli, Javier H., 2021, Fig. 13 in Fig. 12. Majella pristis n in Periclimenaeus djiboutensis Bruce 1970, Zoological Studies 60 (28), pp. 1-20 : 7-8

Cyrtopleura (Scobinopholas) lanceolata (d'Orbigy, 1841 in 1834–1847) ( Fig. 4 )

Pholas lanceolata d'Orbigy, 1841 in 1834–1847, 1841: 497, pl. 77, figs. 18–19.

Barnea lanceolata – Tryon 1862: 208; Ihering 1907: 329; Lamy 1925: 43; Carcelles 1944: 295, pl. 16, fig. 110; Barattini 1951: 256; Barattini and Ureta 1961: 184.

Barnea (Scobinopholas) lanceolata – Lange de Morretes 1949: 49; Gofferjé 1950: 279.

Cyrtopleura (Scobinopholas) lanceolata – Lange de Morretes 1949: 49; Goffergé 1950: 279; Turner 1954: 39–41, pl. 19, figs. 1–3; Olazarri 1962: 51; Figueiras 1962: 64; Rios 1966: 36; Klappenbach 1967: 165; Huber 2010: 475.

Cyrtopleura lanceolata – Turner 1954: 39–41, pl. 19, figs. 1–3; Castellanos 1970: 257; Scarabino 1977: 215; Hoagland and Turner 1981: 130; Scarabino 2003: 242; Scarabino et al. 2006: 396, 2016: 7; Rios 2009: 592, fig. 1633; Dias Passos and Magalhães 2011: 148; Zelaya 2016: 254.

Type locality: Ensenada de Ros, Rio Negro province, Argentina.

Ty p e m a t e r i a l: NHMUK 1854.12.4.654, paralectotypes, 3 specimens; MNHN-IM, unnumbered, probable lectotypes, 4 valves ( Fig. 4A–K ).

Description: Shell: lanceolate, fragile, elongated, equivalve, inequilateral, length up to 70 mm, both ends rounded but with the anterior end slightly angled ( Fig. 4A–D ); umbos well developed sub central but near the anterior third of the shell; umbonal reflections separated from the umbos ( Fig. 4A, C ); pedal gape narrow and elongated; external surface with a weak radial sculpture, usually absent on the posterior slope in adults, in juvenile specimens radial sculpture observed over the entire length; concentric sculpture well developed ( Fig. 4A, C, E, G ); internal surface white; pallial sinus deep and broad, about 60% of shell length ( Fig. 4B, D, F ); pallial line and adductor muscle scar well marked; apophysis short but broad, fragile and flattened at the distal end ( Fig. 4N ); protoplax T-shaped, thin, chitinous, slightly downward curved at its posterior area, closely attached to the muscles; mesoplax calcareous, transverse, composed by two parts, the anterior part inserted into the socket of the umbonal reflection; periostracum yellowish and deciduous.

Mantle cavity organs (Based on Turner, 1954 and museum material): siphons totally fused, protected by a light-brown, papillose, chitinous cover; incurrent siphon with a row of single tentacles surrounding the aperture; excurrent siphon without tentacles; pedal gape and foot elliptical in outline.

Material examined: Uruguay ─ Punta del Este ( MLP 8448, 8449); Argentina ─ Punta Médanos ( MLP 16084, 16900), Ostende ( MACN 20096), Villa Gesell ( MACN 5377), Mar Chiquita ( MACN 26529, 29384), Santa Clara del Mar ( MLP 7781-2), Mar del Plata ( MACN 9361-39, 10234, 10746, 11990), Chapadmalal ( MACN 26246), Miramar ( MACN 1888, 2329, 2387, 15635, MLP 1443), Puerto Quequén ( MLP 2311, 12037), Monte Hermoso ( MACN 1421, 1885, 6619- 14, 9210-13, 11169, 14818), Arroyo Chocorí ( MACN 19950), Puerto Belgrano ( MACN 11168), Bahía Blanca ( MACN 4497), Arroyo Parejas ( MACN 11167), Caleta Brightman ( MACN-INV 16143), Río Colorado ( MLP 1386), Villarino ( MLP 40815), San Blas bay ( MACN 20212), Río Negro mouth ( MACN 20547, MLP 1886, 2709, 4894).

Distribution: From Sao Paulo state, Brazil to San Matías gulf, Argentina ( Turner 1954; Ruhland and Saalfeld 1967; Rios 1994 2009; Scarabino 1977). In this work, specimens from Punta del Este, Uruguay, to Rio Negro mouth were studied. In addition, this taxa had been reported to quaternary deposits of Puerto Belgrano and Mar del Plata ( Figueiras 1962).

Remarks: Cyrtopleura (Scobinopholas) lanceolata has been reported from calcareous rocks and soft substrates ( Rios 1966). No synonyms of this taxa were found in the literature. Although several authors included this species in other genera, such as Pholas and Barnea , the morphology of its shell places it within the genus Cyrtopleura and the subgenus Scobinopholas . Cyrtopleura (S.) lanceolata differ from C. crucigera in showing a more rounded anterior end, lanceolate shell outline, much weaker sculpture and mesoplax in two parts, and from C. (S.) costata by its weak radial sculpture, not observed on the posterior slope, flat apophysis, longer anterior slope and mesoplax in two parts.

Figures

Fig. 4. Cyrtopleura lanceolata. A−H, probable lectotypes, MNHN-IM unnumbered. I−N, examined material, MACN 9361-39. Scale bars: A−M = 1 cm; N = 1 cm.