Purpurocardia leonensis

Pérez, Damián E. & Del Río, Claudia J., 2017, Systematics of the family Carditidae (Bivalvia: Archiheterodonta) in the Cenozoic of Argentina, Zootaxa 4338 (1), pp. 51-84 : 73-74

Purpurocardia leonensis del Río, 1986

Figure 6.6–9

v*1986 Venericardia (Purpurocardia) leonensis del Río, p. 114, pl. 1, fig. 2.

v1994 Venericardia (Purpurocardia) leonensis del Río—del Río, p. 102–104, pl. 1, figs. 8–9.

Type specimen. Holotype CPBA 11651, right valve. Paratypes CPBA 11652 , 12921 and 12926. All from Cerro Prismático (Chubut Province, Puerto Madryn Formation ).

Other material. CPBA 11653–11656, 12922–12925, 12927–12929, 13583–13585 (four left valves and 10 right valves).

Diagnosis. Shell medium-sized with subcircular outline. Posterior area defined by smooth convexity change. Umbo small and pointed. Right anterior tooth very small and strongly inclined posteriorly. Left anterior tooth strongly inclined posteriorly. External sculpture of 24 to 26 high radial ribs.

Description. Shell medium-sized with subcircular to subquadrate outline; dorsal margin slightly convex, gently sloping, posterior margin truncated with a strongly marked angle between it and posterior margin, ventral and anterior margins rounded. Posterior area defined by a smooth change in convexity. Umbo small, pointed, placed near to anterior third of the valve length. Lunule small, convex, prominent and separated by a groove from remaining surface of shell.

Right valve hinge with sinuous ventral edge; anterior tooth small, triangular, narrow, curved and inclined posteriorly; middle tooth very broad and triangular, inclined posteriorly, with broad base, ventrally concave with slightly concave anterior and convex posterior sides, and higher towards apex on lateral view; posterior tooth narrow and straight. Left valve hinge with almost straight ventral edge; anterior tooth strong, broad, triangular and strongly inclined posteriorly; posterior tooth elongate, narrow and curved.

External sculpture of 24 to 26 tripartite radial ribs, high, wide, with a subelliptic transverse section; covered with well-developed nodes of subrectangular transverse section; very reduced paracostal ribs; wide ‘V’-shaped intercostal spaces with. Pallial line one-fifth of total valve height. Inner ventral margin strongly crenulated; crenulations subtriangular, truncated, running along entire margin up to upper tip of posterior adductor muscle scar.

Remarks. This is a relatively rare species which has only been recorded from Cerro Prismático (Puerto Madryn Formation). The presence of a subcircular shell outline, truncated posterior margin, prominent lunule, sinuous right hinge ventral edge, triangular right middle tooth broad and ventrally concave, 25 to 26 wide radial ribs with reduced paracostal ribs allow to confirm the assignment of this species to Purpurocardia .

Purpurocardia leonensis can be distinguished from P. purpurata ( Deshayes, 1854) ( Beu 2006: pl. 18, figs. B, D, E) by having a shell with subcircular outline and more developed posterior area, smaller and pointed umbo, left anterior tooth inclined posteriorly instead of vertical, and higher radial ribs.

Purpurocardia leonensis differs from P. perscrupulosa ( Marwick, 1932) ( Beu & Maxwell 1990: pl. 17, figs. d, e) (lower–middle Miocene, New Zealand) by its subcircular outline, more developed posterior area, left anterior tooth inclined posteriorly, and lower number of radial ribs.

Purpurocardia leonensis shares with P. beata ( Marwick, 1928: figs. 48 and 50) (upper Miocene–upper Pliocene, New Zealand) and P. titirangiensis ( Marwick, 1943) (= Venericardia martini Marwick, 1928 : figs. 52–53) (upper Pliocene–lower Pleistocene, New Zealand) the subcircular outline, but the Patagonian species has a smaller shell with smaller umbo, right anterior tooth more inclined posteriorly and a lower number of radial ribs.

Purpurocardia elegantoides differs from P. southlandica ( Fleming, 1955: fig. 1.11 and 1.12) (upper Miocene, New Zealand) by subcircular outline, more developed posterior area, and smaller umbo.

This species can be distinguished from P. elegantoides by having larger shells with subcircular outline, less defined posterior area, smaller umbo and a higher number of radial ribs.