Pérez and del Río—Danian Carditidae from Argentina
Diagnosis.—Shells with a subquadrate outline. Lunule absent. Right anterior tooth minute; left anterior tooth small, short, and inclined backwards. Radial ribs (25–27) increasing in width towards ventral margin, without paracostal ribs, and with strongly funginated nodes.
Occurrence.—General Roca and Coli Toro Plateau areas (Danian, Roca Formation, Río Negro Province).
Description.—Shell medium-sized to small, subquadrate to subrounded, with rounded anterior and ventral margins, convex dorsal margin, and almost straight posterior margin. Umbones placed near middle of valve length. Lunule absent. Right valve hinge with straight or slightly curved ventral edge; right anterior tooth reduced, thin, straight, in contact with middle tooth; middle tooth triangular, inclined backwards, with wide base, higher than other teeth; posterior tooth straight, thin. Left valve hinge with nearly straight ventral edge; anterior tooth small, short, inclined backwards, with short anterior and convex posterior edges; posterior tooth narrow, slightly curved, higher than anterior tooth, with sharp dorsal tip, ventral surface finely striate. External sculpture of 25–27 radial ribs of triangular transverse section, without paracostal ribs, wider towards ventral margin; high central costal cord with subrectangular funginated nodes, more numerous towards ventral and anterior margins; intercostal spaces of ‘V’-shaped transversal section, each narrower than one radial rib. Pallial line at one-quarter of total valve height. Inner ventral margin strongly crenulate, crenulations triangular, with sharp tips, covering entire margin to dorsal edge of adductor posterior muscle scar.
Etymology.—The specific epithet honors Mario and Luigi, the Mario Bros. brothers, main characters from the popular videogame Mario Bros., in which they collect mushrooms, and it is a reference to the ‘funginate’ nodes of the radial ribs in this species.
Materials.—MACN-Pi 4180, 5758–5762, 5766 (17 left valves, 13 right valves, and one fragment).
Remarks.—The specimen assigned to Glyptoactis feruglioi Petersen, 1946 by Rodríguez et al. (1995, pl. 2, fig. 1) from Cerro Tiltilco is placed in R. mariobrosorum n. sp. The new species differs from G. feruglioi by its less triangular outline with a truncated posterior margin, its smaller hinge, the presence of a right anterior tooth, and its smaller right middle tooth. The new species is placed in Rotundicardia because it has a
R. rotunda (Lea, 1833) (Heaslip, 1968, pl. 22, figs. 8, 9, pl. 23, figs. 1, 2) by its subquadrate shells, smaller right anterior tooth, shorter and smaller left anterior tooth, and radial ribs
subquadrate outline with slightly truncated posterior margin, 25–27 radial ribs covered with funginated nodes, and because it lacks a lunule and paracostal ribs. Glyptoactis Stewart, 1930 (type species V. hadra Dall, 1903, Miocene, Florida, USA) (Heaslip, 1968, pls. 27–29), the genus where Rodríguez et al. (1995) placed these shells, has a more triangular outline, with larger and more prominent umbones, fewer radial ribs (19–20) covered with small subrectangular nodes. Rotundicardia mariobrosorum n. sp. differs from
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becoming wider towards the ventral margin. Rotundicardia diversidentata (Meyer, 1885) (Heaslip, 1968, pl. 23, figs. 3–8, Jackson and Ocala Limestone formations, late Eocene, USA) differs from R. mariobrosorum n. sp. in having the same characters as R. rotunda, and a lunule and less pronounced nodes.
R. eoa (Gardner, 1935) (Heaslip 1968, pl. 22, figs. 1, 2) and R. crenaea (Gardner, 1935) (Heaslip, 1968, pl. 22, figs. 3, 4) (Kincaid Formation, late Danian, USA) because both the latter species have fewer radial ribs (~23) covered with less pronounced nodes, and have paracostal ribs, that are absent from R. mariobrosorum n. sp. Rotundicardia flabellum (Harris, 1919) (Heaslip, 1968, pl. 22, figs. 6, 7, Weches and Yegua formations, middle Eocene,
Rotundicardia mariobrosorum can be distinguished from
Kendrick, 2008, fig. 1.5, Lower Browns Creek, Upper Browns Creek, Blanche Point formations and Southern Carnavon Basin, middle–late Eocene, Australia) can be distinguished from R. mariobrosorum because the South American species has a more subquadrate shape and radial ribs with more prominent nodes.
Darragh, 1994 (Darragh, 1994, fig. 6E, 6F, 6I–6L, Pebble Point and Kings Park formations, late Paleocene, Australia) by having a slightly truncated posterior margin instead of the expanded posterior margin that characterizes the Australian species. Rotundicardia latissima (Tate, 1886) (Darragh and
Genus Cardites Link, 1807
Type species.—Chama antiquata Linnaeus, 1758 (by original designation). Miocene–Recent of Europe and Northern Africa.
Diagnosis.—Carditid with very convex shell, subtriangular to subrounded in shape with a truncated posterior margin. Umbones prominent. Lunule convex. Right anterior tooth extremely faint; absent in some species. Radial ribs wide, sculptured with beaded or rectangular nodes.
Remarks.—The key character of Cardites is the presence of a very faint right anterior tooth (Link, 1807; Chavan, 1969), absent according to other authors (Dall, 1902; Lamy, 1921). This tooth could be present with varying degrees of develop- ment within different species of the genus (see for examples Lamy, 1921, p. 202; Chavan, 1969, fig. E56.1; Huber, 2010, p. 251). The diagnoses provided by Dall (1902), Lamy (1921), and Chavan (1969) are incomplete for a definition of Cardites. Because of this, we give an emended diagnosis herein. The oldest records for Cardites are C. dertopartschii (Sacco,
1899) and C. partschii (Goldfuss, 1840) from the Burdigalian (early Miocene) of the Vienna Basin (Sieber, 1954). Cardites has a wide stratigraphical and geographical range, and has been cited fromMiocene of Europe (Jimenez and Braga, 1993; Lacour et al., 2002) andNorthAfrica (Freneix et al., 1987), fromthe Pliocene of
USA) and R. carsonensis (Dall, 1903) (Heaslip, 1968, pl. 23, figs. 9, 10, Red Bluff Formation, early Oligocene, USA and from an unnamed formation, early Oligocene, Mexico) are distinguished from R. mariobrosorum by the presence of a lunule, by having a larger anterior right tooth, and by having radial ribs of equal width throughout the ontogeny. Rotundicardia mariobrosorum differs from R. petraea
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