Scalaricardita Sacco, 1899

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 : 74-75

Genus Scalaricardita Sacco, 1899

Type species. Venericardia scalaris J. de C. Sowerby, 1825 (pl. 490, fig. 3) (by original designation), upper Miocene-Pliocene of the Vienna Basin, Italy and Poland; Pliocene of North Sea Basin.

Diagnosis. Carditid with subtriangular to subcircular outline. Small umbo. Lunule long and flat. Right middle tooth triangular and broad, left anterior tooth straight. External sculpture of 23 to 27 wide radial ribs, covered by closely-spaced subrectangular nodes with wide intercostal spaces sometimes reduced to a very narrow groove.

Included species. S. camaronesia ( Ihering, 1907) (lower Miocene, Argentina), S. compacta ( Tate, 1886) (middle Miocene, Australia), S. laciarina ( Feruglio, 1954) (lower Pliocene, Argentina), S. miniscula ( Bartrum & Powell, 1928) (upper Pliocene, New Zealand) and S. subcompacta ( Chapman & Crespin, 1928) (lower Pliocene, Australia).

Remarks. Sacco (1899) erected the genus in order to separate Venericardia scalaris from Miodontiscus Dall, 1903 , and Coripia de Gregorio, 1885 ; which comprise very small-sized Cenozoic carditids from Italy. Sacco also indicated that Scalaricardita has a smaller shell with less circular outline, less convex dorsal margin, more pronounced radial ribs with subrectangular instead of subrounded nodes, provided with smaller and less curved right middle tooth and less curved right posterior tooth. Sacco (1899) mentioned that V. scalaris could be related to Cyclocardia Conrad, 1867 by similarities in outline and shell sculpture, and later Dall (1902; 1903) and Thiele (1935) suggested a possible synonymy between Scalaricardita and Cyclocardia . Scalaricardita can be separated from Miodontiscus and Coripia , by having a more rounded shell with subcentrally placed umbo, less radial ribs with subrectangular nodes and narrower intercostal spaces.

Scalaricardita differs from Pleuromeris Conrad, 1867 (type species P. decemcostata Conrad, 1867 ; Pliocene– Pleistocene of USA) by having a less triangular outline and a higher number of radial ribs separated by narrower intercostal spaces.

The genus is represented in the Miocene and Pliocene of Europe by the type species ( Sacco 1899; Glibert & Van der Poel 1970; Raffi et al. 1985; Studencka 1986; Janssen & Moerdijk 2004) and Australia ( Darragh, 1970) by S. compacta ( Tate, 1886) (Mudy Creek Formation, middle Miocene) and S. subcompacta ( Chapman & Crespin, 1928) (Sorrento Bore, lower Pliocene). Pleuromeris miniscula Bartrum & Powell, 1928 (Kaawa Creeks Beds, upper Pliocene, New Zealand) may be belongs to Scalaricardita since it has a subcircular outline, umbo subcentrally placed, and by having 22 radial ribs with subrectangular nodes and very narrow intercostal spaces.