Neuquina Basin

Carditids included in the present paper come from the Roca Formation exposed at Malargüe (Mendoza Province), Cerros Bayos (La Pampa Province) and the surroundings of the city of General Roca (Río Negro Province), and from the Jagüel Formation exposed at Opaso section (Neuquén Province) (Fig. 1.1, 1.2).

Fossils from General Roca have been recorded in the NP1–NP4 biozones recognized in Cantera Cholino, Picada Sísmica and Zanjón Roca sections, where abundant internal molds of carditids have been collected (Fig. 2.1–2.3). Assemblages constitute parauthochtonous accumulations. Carditids are associated with dense concentrations of the gastropod Rostellaria rothi Ihering, Reference Ihering1903 and the oyster Cubistostrea ameghinoi (Ihering, Reference Ihering1902) (Cantera Cholino samples 15 and 17, respectively), and of turritellids in Picada Sísmica, where the carditids are found alone with the infaunal soft-bottom dewelling bivalves Neilo sp. and Dosinia burckhardti Ihering, Reference Ihering1907 (del Río et al., Reference del Río, Concheyro and Martínez2011).

Figure 2

Lithological sections. (1) Cantera Cholino. (2) Zanjón Roca. (3) Puesto Ñancucheo. (4) Cerro Tiltilco. (5) Puesto Carmelo Ibañez. (6) Picada Sísmica. (7) Puesto Nahuel Cheo. (8) Cerros Bayos. (9) Puesto Pircala. (10) Puesto Álvarez, 1=Claibornicardia paleopatagonica, 2=Rotundicardia mariobrosorum n. sp., 3=Cardites feruglioi, 4=Kalelia burmeisteri, 5=‘Venericardia’ iheringi; (1, 2, 4–7) after del Río, Reference del Río2012; (8) after del Río et al., Reference del Río, Martínez, Stilwell and Concheyro2007; (10) after Masiuk, Reference Masiuk1967.

Carditids are rare at Cerro Bayos, where only one species has been found. Material comes from basal (CB31 and CB32 samples) and uppermost limestones (CB47 samples) of the Roca Formation where the NP1 and NP3 biozones are identified, respectively (Fig. 2.8). In the basal limestones, fossils are infrequent, carditids are rare, and the bivalves Pycnodonte (Phygrea) burckhardti (Böhm, Reference Böhm1903), Delectopecten, Parvamussium, and unidentified veneroids dominate the fauna. In contrast, horizons at the top of the section are highly fossiliferous, and comprise up to 8 m thick amalgamated yellowish, massive limestones with a dense accumulation of Cubitostrea ameghinoi, Turritella spp. and subordinate representatives of the carditids and the bivalves Gryphaostrea callophyla (Ihering, Reference Ihering1903) and Jupiteria sp. (del Río et al., Reference del Río, Martínez, Stilwell and Concheyro2007).

Strata exposed in the vicinities of Puesto Pircala (Mendoza Province, Neuquina Basin) record the only Maastrichtian carditids mentioned in this paper and only a brief explanation will be provided herein (Fig. 2.9). These exposures comprise 30 m of intercalation green and white mudstones and highly fossiliferous yellowish limestones with the gastropod ‘Turritella’ sp., and the bivalves Musculus aprilis (Feruglio, Reference Feruglio1935), Ambigostrea clarae (Ihering, Reference Ihering1907), Amphidonte mendozana Ihering, Reference Ihering1907, Pinna sp., Camptonectes sp., Acesta sp., Yoldia? sp., Paraesa? sp. and Pterotrigonia sp.

Cañadón Asfalto Basin

Carditids are very abundant in the Roca Formation exposed in the Bajo de Colitoro Grande, Bajo Hondo, and Bajo Lenza Niyeu (Río Negro Province) (Fig. 1.3). However, while they are rare components of the fauna in the uppermost horizons of the Lefipán Formation at the middle Chubut River, they are common bivalves in the Salamanca Formation exposed in Sierra de los Guanacos area (Chubut Province).

Fossiliferous horizons in the Bajo Hondo and Bajo Lenza Niyeu are exposed at Puesto Nahuel Cheo and Puesto Carmelo Ibañez sections (Fig. 2.5, 2.6). Here, carditids come from hard, thin, pinkish massive grainstones, constituted by amalgamated, multi-event shell beds with internal discontinuities. Cardites feruglioi (Petersen, Reference Petersen1946) and a new species of Rotundicardia (Heaslip, Reference Heaslip1968) herein described are commonly associated with dense concentrations of Pycnodonte (Phygraea) sarmientoi Casadío, Reference Casadío1998, and Ostrea neuquena Ihering, Reference Ihering1907 or Turritella malaspina Ihering, Reference Ihering1903. In both cases a rich gastropod fauna is represented by Tejonia tapiae (Feruglio, Reference Feruglio1935), Microfulgur concheyroae del Río, Reference del Río2012, Heteroterma carmeloi del Río, Reference del Río2012, Rocalaria alani del Río, Reference del Río2012, Cavoscala sp., Gyroscala daniana del Río, Reference del Río2012, Sulcobuccinum prominentum del Río, Reference del Río2012, Austrophaera patagonica (Feruglio, Reference Feruglio1936) and by the echinoid Cidarina lenzaniyeuensis del Río, Reference del Río2012 (del Río, Reference del Río2012).

Carditids from Bajo del Colitoro Grande come from Cerro Tiltilco and Puesto Ñancucheo sections where the uppermost horizons (Fig. 2.4, 2.7), consisting of thick ochreous and whitish massive coquinas, yield Claibornicardia paleopatagonica (Ihering, Reference Ihering1903), R. mariobrosorum n. sp., C. feruglioi, and Kalelia burmeisteri (Böhm, Reference Böhm1903). Associated with the carditids are the bivalves Glycymeris feruglioi Celeste, Reference Celeste1940, Ostrea neuquena Ihering, Reference Ihering1907, Panopea spp., and the gastropods Tejonia tapiae (Feruglio, Reference Feruglio1935), Priscofiscus cf. P. gracilis (Wilckens, Reference Wilckens1905), Sulcobuccinum prominentum del Río, Reference del Río2012, and Austrophaera patagonica (Feruglio, Reference Feruglio1936) (del Río, Reference del Río2012).

The Salamanca Formation exposed in the surroundings of Sierra de los Guanacos (Fig. 1.1) consists of an intercalation of siltstones, sandstones and coquinas with a poorly diversified fauna (Chebli and Serraioto, Reference Chebli and Serraioto1974) with abundant representatives of C. paleopatagonica associated with the bivalves Nucula pervicax Feruglio, Reference Feruglio1936, Ostrea neuquena, Bathytormus chubutensis (Feruglio, Reference Feruglio1936), and the gastropods ‘Turritella’ ameghinoi Ihering, Reference Ihering1903, Darwinices claudiae Griffin and Pastorino, Reference Griffin and Pastorino2013, Pseudamaura dubia (Petersen, Reference Petersen1946), ‘Cominella iheringi’ Feruglio, Reference Feruglio1936, Austrophaera patagonica (Feruglio, Reference Feruglio1936), Gyroscala daniana del Río, Reference del Río2012, Turritella malaspina Ihering, Reference Ihering1903 (del Río and Martínez, Reference del Río and Martínez2015).

San Jorge Basin

The studied material was recorded by C. Ameghino from Río Chico, in an area supposedly situated 50 km south of Puesto Alvarez (Fig. 2.10) (Chubut Province). This section was assigned to the Salamanca Formation and consists of an intercalation of gray or yellow calcareous sandstones with siltstones and whitish coquinas. The species K. burmeisteri is associated with the bivalves Glycymeris feruglioi, Panopea thomasi Ihering, Reference Ihering1914, and the gastropods Turritella aff. T. soaresana Hartt in White, Reference White1887, Polinices sp., Arrhoges sp. and Cimomia camachoi Masiuk, Reference Masiuk1967.

Remarks

The systematics of carditids is complex because there is no consensus about the distinction among genera and subgenera. On one hand, for some authors, the family includes a few genera (Venericardia Lamarck, Reference Lamarck1801 and Cardita Bruguière, Reference Bruguière1792) with a large number of subgenera (e.g., Megacardita Sacco, Reference Sacco1899; Venericor Stewart, Reference Stewart1930; or Claibornicardia Stenzel and Krause, Reference Stenzel and Krause1957). Other authors treat some of these subgenera as genera (for a comparison, see Sacco, Reference Sacco1899; Dall, Reference Dall1903; Chavan, Reference Chavan1969; Moore, Reference Moore1992; McClure and Lockwood, Reference McClure and Lockwood2015). The use of subgenera implies close phylogenetic relationships, most of which are poorly understood at present. Therefore, until a complete quantitative phylogenetic study of the family is performed, we consider all carditid genera or subgenera previously proposed to have generic status, thereby discarding all phylogenetic inferences. McClure and Lockwood (Reference McClure and Lockwood2015) proposed that Claibornicardia and Rotundicardia are possible paraphyletic genera based on a phylogenetic study of some GCP carditid species. Because they included relatively few species of both taxa in their analysis, we prefer to keep the monophyletic status until a complete revision is performed.

Chavan (Reference Chavan1969) outlined a subfamiliar classification for the Carditidae on the basis of taxonomic criteria. He recognized seven subfamilies, six newly introduced by him: Carditinae, Carditamerinae, Miodomeridinae, Palaeocarditinae, Venericardiinae, Carditesinae, and the previously proposed Thecaliinae Dall, Reference Dall1903, based mainly on shell shape and hinge morphology. Members of the planicostates and alticostates were indistinctively included in Carditamerinae, Venericardiinae, or Carditesinae by Chavan (Reference Chavan1969). In this paper, we reject the subfamiliar classification proposed by Chavan (Reference Chavan1969) because his scheme ignored the phylogenetic proposals of other authors (Gardner and Bowles, Reference Gardner and Bowles1939; Heaslip, Reference Heaslip1968), as indicated by the analysis of Pérez and del Río (Reference Pérez and del Río2016), and prefer these proposals instead.

Genus Claibornicardia Stenzel and Krause, Reference Stenzel and Krause1957

Type species

Cardita alticostata Conrad, Reference Conrad1833 (by original designation). Gosport Sand, McBean and Black Mingo formations, early–middle Eocene of Alabama, United States of America (USA).

Diagnosis

Carditid with a highly convex shell and an elongated subrectangular outline, posterior area defined by a change in the convexity. Ventral margin of right hinge sinuous. Right anterior tooth thin dorsally or anteriorlly placed to the anterior socket for the left anterior tooth, left anterior tooth broad and triangular. External sculpture of 28–33 tripartite radial ribs covered with nodes. Nodes and paracostal ribs suppressed in advanced members of the genus (modified from Heaslip, Reference Heaslip1968, p. 98).

Remarks

The genus Claibornicardia was erected by Stenzel and Krause in Stenzel and Krause, Reference Stenzel and Krause1957 to include few carditids from the middle Eocene of the GCP geological province (C. alticostata [Conrad, Reference Conrad1833], C. complexicostata [Meyer and Aldrich, Reference Meyer and Aldrich1886], C. nasuta [Dall, Reference Dall1890], C. sillimani [Lea, Reference Lea1833], and C. trapaquara [Harris, Reference Harris1895]) and C. acuticostata (Lamarck, Reference Lamarck1806) from the Eocene of the Paris Basin (France). According to Stenzel and Krause (Reference Stenzel and Krause1957), the key characters of the genus are the elongate-rectangular outline with a faint posterior area, and the development of tripartite radial ribs.

Heaslip (Reference Heaslip1968) reviewed the genus, and extended its stratigraphic range in the southeastern region of the USA from the early Eocene to the middle Oligocene with the addition of several new species (C. blandingi [Conrad, Reference Conrad1830]; C. coloradonis [Harris, Reference Harris1919]; C. linguinodifera Heaslip, Reference Heaslip1968; C. natchitoches [Harris, Reference Harris1919]; C. perantiqua [Conrad, Reference Conrad1865]; and C. trapaquaroides Heaslip, Reference Heaslip1968), and synonymized C. sillimani with C. alticostata, stating that it is a case of sexual dimorphism. All American species are characterized by variable outlines, with diverse degrees of elongation and posterior margin acumination (C. nasuta, C. trapaquara, and C. trapaquaroides) and/or ventral margin acumination (C. blandingi, C. complexicostata, and C. perantiqua). Particularly, C. alticostata shows strong morphological variation (as shown by Heaslip, Reference Heaslip1968, pl. 26, figs. 6–11). Cases of allometric growth are recognized within carditids (Stanley, Reference Stanley1972), where the shell outlines can vary throughout ontogeny. Combining allometry with sexual dimorphism and the wide geographical distribution of certain species (e.g., C. alticostata), it is possible that the true intraspecific variation of Claibornicardia is misunderstood and some proposed American species are part of the variation of other species.

Moore (Reference Moore1992) included within Claibornicardia four species from California and Baja California: C. keenae (Verastegui, Reference Verastegui1953) (late Paleocene), C. domenginica (Vokes, Reference Vokes1939), C. marksi (Verastegui, Reference Verastegui1953), and C. sandiegoensis (Hanna, Reference Hanna1927), the last three all being Eocene. These taxa have less elongate outlines and more convex shells than the eastern American species, but have the characteristic tripartite radial ornamentation.

Claibornicardia aalterensis Vervoenen and van Nieulande, Reference Vervoenen and van Nieulande2010, C. asperrima (Wood, Reference Wood1861), C. carinata (Sowerby, Reference Sowerby1821), and C. obovata (Wood, Reference Wood1861), from the Eocene of England, France, and Belgium, also have been placed within Claibornicardia (Pacaud and Le Renard, Reference Pacaud and Le Renard1995; Tracey et al., Reference Tracey, Todd, Le Renard, King and Goodchild1996; Vervoenen and van Nieulande, Reference Vervoenen and van Nieulande2010). These species, together with C. acuticostata, should potentially be assigned to a different genus converging with the American species, because they have less elongated outlines with a less well defined posterior area and a fewer radial ribs. There are other records from the Eocene of Colombia and Jamaica that are doubtfully assigned to C. alticostata because they are based on incomplete specimens in which the diagnostic characters cannot be recognized (Anderson, Reference Anderson1928; Cox, Reference Cox1941). Kafanov et al. (Reference Kafanov, Ogasawara and Marincovich2001) recorded C. keenae from the late Paleocene Getkilninskaya Formation (Kamchatka, Russia; Kafanov and Ogasawara, Reference Kafanov and Ogasawara2006). This record, together with C. keenae from the late Paleocene Lodo Formation (California, USA, Johnson and Graham, Reference Johnson and Graham2007), are the most ancient records known for the genus Claibornicardia.

Claibornicardia paleopatagonica (Ihering Reference Ihering1903)

Figure 3.1, 3.2, 3.4, 3.5

Figure 3

Claibornicardia paleopatagonica (Ihering, Reference Ihering1903) (1, 2, 4, 5): (1) external view of left valve, holotype MACN-Pi 360, from ‘Río Chico’; (2) internal view of left valve, MACN-Pi 5197, from Puesto Ramírez; (4) external view of right valve, MACN-Pi 5197, from Puesto Ramírez; (5) internal view of right valve, MACN-Pi 5197, from Puesto Ramírez. Rotundicardia mariobrosorum n. sp. (3, 6–10): (3) detail of sculpture, MACN-Pi 5762, from Puesto Carmelo Ibañez: (6) external view of left valve, holotype CPBA 17276, from Cerro Tiltilco; (7) internal view of left valve, holotype CPBA 17276, from Cerro Tiltilco; (8) external view of right valve, Paratype MACN-Pi 5758, from Puesto Ñancucheo; (9) internal view of right valve, Paratype MACN-Pi 5758, from Puesto Ñancucheo; (10) external view of left valve, Paratype MACN-Pi 5758, from Puesto Ñancucheo. All scale bars represents 10 mm.

1903 Cardita paleopatagonica Reference IheringIhering, p. 215, pl. 2, fig. 12.

1907 Venericardia paleopatagonica (Ihering); Reference IheringIhering, p. 47.

1914 Venericardia paleopatagonica (Ihering); Reference IheringIhering, p. 44.

1936 Venericardia paleopatagonica (Ihering); Reference FeruglioFeruglio, p. 232, pl. 23, figs. 28, 29.

1938b Venericardia paleopatagonica (Ihering); Reference Fossa ManciniFossa Mancini, p. 261.

1977 Venericardia camachoi Reference VigilanteVigilante, p. 20, pl. 1, fig. 6.

1987 Venericardia paleopatagonica (Ihering); Reference Farinati, Quattrocchio and LabudíaFarinati et al., p. 154, pl. 1, fig. 5.

1995 Glyptoactis paleopatagonica (Ihering); Reference Rodríguez, Getino and SepúlvedaRodríguez et al., p. 243, pl. 2, fig. G.

1995 Glyptoactis sp. (Ihering); Reference Rodríguez, Getino and SepúlvedaRodríguez et al., p. 243, pl. 2, fig. H.

1996 Cardita paleopatagonica Ihering; Reference ParodizParodiz, p. 246.

2012 Venericardia (Pacificor) iheringi (Böhm); Reference Scasso, Aberhan, Ruiz, Weidemeyer, Medina and KiesslingScasso et al., p. 43, fig. 4G.

Type specimen

Holotype MACN-Pi 360, articulated shell from ‘Río Chico’ (Chubut Province, Salamanca Formation).

Diagnosis

Outline subrectangular to subovate with rounded posterior margin. Lunule deep. Right anterior tooth inclined backwards, placed on anterior side of left anterior socket. Radial ribs (30–33) sculptured with closely spaced subcircular nodes and with narrow intercostal spaces.

Occurrence

General Roca and Coli Toro Plateau areas (early Danian, Roca Formation, Río Negro Province), Opaso (early Danian, Jagüel Formation, Neuquén Province), and Río Chico’s area (early Danian, Salamanca Formation, Chubut Province).

Description

Shell thick, medium-sized, subrectangular to subovate in anterior-posterior direction, with elongate outline; posterior rounded, slightly curved ventral and gently inclined dorsal margins; posterior area defined by smooth convexity change starting from the eighth rib. Small umbones placed near anterior fifth of valve length. Lunule small, vertical, slightly concave, demarcated by an incised groove from remaining surface of shell, sculptured with fine commarginal growth lines.

Right valve hinge with sinuous ventral edge below middle tooth; small, short anterior tooth inclined backwards, thin, parallel to middle tooth, placed on anterior side of left anterior socket; middle tooth triangular, inclined strongly backwards, with narrow base, fine striations on dorsal surface, higher towards apex in lateral view; posterior tooth thin, slightly curved, taller than anterior one but shorter than middle tooth.

Left valve hinge with almost straight ventral edge; anterior tooth elongate, triangular, inclined backwards, slightly curved, with straight anterior and curved posterior sides; posterior tooth elongate, narrow, straight, with narrow base and acute apex, equal in height to anterior tooth.

External sculpture with 30–33 radial ribs having a subtriangular transverse section, widening in ventral direction; elevated central costal rib covered by nodes with subcircular transverse section; smooth paracostal ribs of rounded transverse section, as wide as central rib; narrow intercostal spaces delimited by deep, narrow groove; posterior area sculptured with eight weaker, less-high ribs, with less pronounced tripartition, first three ribs with stronger, more elevated nodes than the remainder.

Pallial line at a quarter of total valve height. Inner ventral margin strongly crenulated; crenulations triangular, truncated, covering entire margin to posterior adductor muscle scar, becoming smaller over posterior.

Remarks

Ihering (Reference Ihering1903) described C. paleopatagonica based on a shell with conjoined valves from ‘Río Chico’ (Salamanca Formation), stating that the type specimen did not allow the description of hinge features. Ihering (Reference Ihering1907) mentioned other specimens of C. paleopatagonica from ‘Rocanense’ exposures from an unspecified locality, but only the type specimen is present in Ihering’s collection.

Feruglio (Reference Feruglio1936, pl. 23, figs. 28, 29) described and illustrated specimens from Puesto Ramírez (Danian, Salamanca Formation, Chubut Province) and later, Vigilante (Reference Vigilante1977, pl. 1, fig. 6) assigned one of the juvenile specimens collected by Feruglio to V. camachoi Vigilante, Reference Vigilante1977. Both authors referred their species to Venericardia Lamarck, Reference Lamarck1801 (type species V. imbricata Lamarck, Reference Lamarck1801, Eocene, Paris Basin) (see La Perna et al., Reference La Perna, Mandic and Harzhauser2017, fig. 3). However, C. paleopatagonica is placed in Claibornicardia because of its subrectangular outline, sinuous ventral hinge margin, thin right anterior teeth, and the presence of wide paracostal ribs with narrow intercostals spaces.

Rodríguez et al. (Reference Rodríguez, Getino and Sepúlveda1995, pl. 2, figs. G, H) illustrated C. paleopatagonica from Cerro Tiltilco (Roca Formation, Río Negro Province), and included it in Glyptoactis Stewart, Reference Stewart1930, (type species V. hadra Dall, Reference Dall1903, Miocene, Florida, USA) (Heaslip, Reference Heaslip1968, pl. 27–29), but this genus has a triangular outline, larger and more recurved umbones, a deeper lunule with the ventrally projecting lunular margin, right hinge ventral edge inverted ‘V’-shaped, right middle and left posterior teeth more curved, fewer radial ribs with wider paracostal ribs, and narrower intercostal spaces.

Claibornicardia paleopatagonica differs from C. alticostata (Stenzel et al., 1957, pl. 13, figs. 1–9; Heaslip, Reference Heaslip1968, pl. 26, figs. 6–11) by its rounded posterior margin, deeper lunule, weaker left anterior tooth, a right anterior tooth that is inclined backwards and placed on the anterior side of the left anterior socket, and by its stronger radial nodes. Juvenile specimens of C. paleopatagonica have subquadrate outlines, while adults are more elongate. The same variation can be observed in C. alticostata (syntypes ANSP 30562 include elongate adults and subquadrate juveniles) (Stenzel et al., 1957).

Species from the middle Eocene of the USA are mainly distinguished from each other and from C. paleopatagonica by their outlines. Claibornicardia linguinodifera Heaslip, Reference Heaslip1968 (Stenzel et al., 1957, pl. 14, figs. 6–11; Heaslip, Reference Heaslip1968, pl. 24, figs. 1, 2; Bashi and Reklaw formations), C. coloradonis (Harris, Reference Harris1919) (Heaslip, Reference Heaslip1968, pl. 24, figs. 3–6; Weches, Wautubbee, and Reklaw formations), and C. natchitoches (Harris, Reference Harris1919) (Heaslip, Reference Heaslip1968, pl. 25, figs. 4–7; Weches Formation) have less elongated outlines, with truncated posterior margins, wide intercostal spaces, and more closely spaced nodes than C. paleopatagonica. Claibornicardia perantiqua (Conrad, Reference Conrad1865) (Heaslip, Reference Heaslip1968, pl. 25, figs. 8–11; Shark River Formation), C. trapaquara (Harris, Reference Harris1895) (Stenzel et al., 1957, pl. 14, figs. 6–11; Heaslip, Reference Heaslip1968, pl. 24, fig. 8, pl. 25, figs. 1–3; Stone City Beds), and C. trapaquaroides Heaslip, Reference Heaslip1968 (Heaslip, Reference Heaslip1968, pl. 24, fig. 7; Weches Formation) can be distinguished from the Patagonian species because their shells have a more acuminated postero-ventral margin, less rounded nodes, and wider intercostal spaces.

Claibornicardia paleopatagonica differs from C. complexicostata (Meyer and Aldrich, Reference Meyer and Aldrich1886) (Stenzel et al., 1957, pl. 15, figs. 1–4; Heaslip, Reference Heaslip1968, pl. 26, figs. 3–5; Wautubbe Formation) by having a subrectangular to subovate shell instead of the subtriangular outlines of the American species.

Claibornicardia blandingi (Conrad, Reference Conrad1830) (Heaslip, Reference Heaslip1968, pl. 26, figs. 1, 2; Lower Santee Limestone Formation) and C. paleopatagonica have similar shell-shapes, but can be distinguished by the larger shells sculptured with a greater number of radial ribs in the Patagonian species.

Claibornicardia paleopatagonica can be distinguished from C. keenae (Verastegui, Reference Verastegui1953) (Moore, Reference Moore1992, pl. 8, figs. 6, 8, 10, 12, 13, 15; Lodo Formation, late Paleocene–early Eocene, California, USA, and Getkilninskaya Formation, late Paleocene, Russia) by having a deeper lunule, and more numerous radial ribs.

Genus Rotundicardia Heaslip, Reference Heaslip1968

Type species

Venericardia rotunda Lea, Reference Lea1833 (by original designation). Gosport Sand, Lisbon, Wautubbee, McBean, Cook Mountain, Weches and Yegua formations, middle Eocene of the USA and Laredo Formation, middle Eocene of México.

Diagnosis

Carditid with a moderately convex shell, subrounded outline, and slightly truncated posterior margin. Umbones small, placed subcentrally. Lunule reduced or absent. Right middle tooth prominent, broad; left anterior tooth strong, triangular. Radial ribs (25–26) high, covered with funginate nodes, and paracostal ribs reduced or absent in many species (modified from Heaslip, Reference Heaslip1968, p. 90).

Remarks

According to Heaslip (Reference Heaslip1968), the main features of Rotundicardia are the subrounded shell shape with centrally placed umbones, and the funginated nodes. Heaslip (Reference Heaslip1968) included seven species from the GCP in Rotundicardia: R. carsonensis (Dall, Reference Dall1903), R. crenaea (Gardner, Reference Gardner1935), R. diversidentata (Meyer, Reference Meyer1885), R. eoa (Gardner, Reference Gardner1935), R. eutawcolensis (Harris, Reference Harris1919), R. flabellum (Harris, Reference Harris1919), and R. rotunda (Lea, Reference Lea1833). He also recognized the presence of sexual dimorphism within R. rotunda and R. diversidentata, identified by the development in males of less convex shells than in females, which are more strongly sculptured.

Beal (Reference Beal1948) recorded Venericardia cf. V. rotunda (Tepetate Formation, middle Eocene, Baja California, Mexico) and Woodring (Reference Woodring1982) recorded Rotundicardia sp. for the late Eocene of Panamá. Darragh (Reference Darragh1994) included two species from Australia within Rotundicardia: R. petraea (Darragh, Reference Darragh1994) from the middle Paleocene, and R. latissima (Tate, Reference Tate1886) from the middle Eocene. The latter was placed within Fasciculardia by Maxwell (Reference Maxwell1969).

The oldest known record for the genus is the late Danian R. crenaea (Gardner, Reference Gardner1935) from the Kincaid Formation (Tehuacana Member, Texas, USA), assigned to this age by Barnes et al. (Reference Barnes, Hartmann and Scranton1992).

Rotundicardia mariobrosorum new species

Figure 3.3, 3.6–3.10

1995 Glyptoactis feruglioi (Petersen): Reference Rodríguez, Getino and SepúlvedaRodríguez et al., p. 243, pl. 2, fig. 1.

Type specimens

Holotype CPBA 17276, one left valve from Cerro Tiltilco (Río Negro Province). Paratype MACN-Pi 5758, right and left valve from Puesto Ñancucheo (Río Negro Province).

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.

Remarks

The specimen assigned to Glyptoactis feruglioi Petersen, Reference Petersen1946 by Rodríguez et al. (Reference Rodríguez, Getino and Sepúlveda1995, 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 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, Reference Stewart1930 (type species V. hadra Dall, Reference Dall1903, Miocene, Florida, USA) (Heaslip, Reference Heaslip1968, pls. 27–29), the genus where Rodríguez et al. (Reference Rodríguez, Getino and Sepúlveda1995) 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 R. rotunda (Lea, Reference Lea1833) (Heaslip, Reference Heaslip1968, 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 becoming wider towards the ventral margin. Rotundicardia diversidentata (Meyer, Reference Meyer1885) (Heaslip, Reference Heaslip1968, 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.

Rotundicardia mariobrosorum can be distinguished from R. eoa (Gardner, Reference Gardner1935) (Heaslip Reference Heaslip1968, pl. 22, figs. 1, 2) and R. crenaea (Gardner, Reference Gardner1935) (Heaslip, Reference Heaslip1968, 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, Reference Harris1919) (Heaslip, Reference Heaslip1968, pl. 22, figs. 6, 7, Weches and Yegua formations, middle Eocene, USA) and R. carsonensis (Dall, Reference Dall1903) (Heaslip, Reference Heaslip1968, 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 Darragh, Reference Darragh1994 (Darragh, Reference Darragh1994, 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, Reference Tate1886) (Darragh and Kendrick, Reference Darragh and Kendrick2008, 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.

Genus Cardites Link, Reference Link1807

Type species

Chama antiquata Linnaeus, Reference Linnaeus1758 (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, Reference Link1807; Chavan, Reference Chavan1969), absent according to other authors (Dall, Reference Dall1902; Lamy, Reference Lamy1921). This tooth could be present with varying degrees of development within different species of the genus (see for examples Lamy, Reference Lamy1921, p. 202; Chavan, Reference Chavan1969, fig. E56.1; Huber, Reference Huber2010, p. 251). The diagnoses provided by Dall (Reference Dall1902), Lamy (Reference Lamy1921), and Chavan (Reference Chavan1969) 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, Reference Sacco1899) and C. partschii (Goldfuss, Reference Goldfuss1840) from the Burdigalian (early Miocene) of the Vienna Basin (Sieber, Reference Sieber1954). Cardites has a wide stratigraphical and geographical range, and has been cited from Miocene of Europe (Jimenez and Braga, Reference Jimenez and Braga1993; Lacour et al., Reference Lacour, Lauriat-Rage, Saint Martin, Videt, Nerandeau, Goubert and Bongrain2002) and North Africa (Freneix et al., Reference Freneix, Saint Martin and Moissette1987), from the Pliocene of Panamá (Collins and Coates, Reference Collins and Coates1999) and Ecuador (Olsson, Reference Olsson1941), and from the Pleistocene of East Asia (Cox, Reference Cox1931), North Africa (El-Sorogy, Reference El-Sorogy2002), Australia (McNamara and Kendrick, Reference McNamara and Kendrick1994), Europe (Menesini and Ughi, Reference Menesini and Ughi1982), and Ecuador (Olsson, Reference Olsson1964). Most of these records have never been reviewed, and a few of these records may not be Cardites. For example, La Perna et al. (Reference La Perna, Mandic and Harzhauser2017) recently placed the species C. ignoratus (Cossman and Peyrot, Reference Cossmann and Peyrot1912) in Megacardita Sacco, Reference Sacco1899.

The only reference to Cardites from the USA was provided by Whitfield (Reference Whitfield1885), who mentioned C. antiquatus as occurring in the Shark River Formation (Eocene of New Jersey). However, Palmer and Brann (Reference Palmer and Brann1965) pointed out that this record mistakenly confused the name with Claibornicardia perantiqua (Conrad, Reference Conrad1865).

Huber (Reference Huber2010) suggested that living species referred to Cardites include species belonging to at least two different genera. He recognizing a group of elongated species from America, including C. floridanus (Conrad, Reference Conrad1838), C. grayi (Dall, Reference Dall1903), and C. laticostatus (Sowerby, Reference Sowerby1833), and another group composed of species with triangular and subrounded shells from Europe and Asia, including C. antiquatus (Linnaeus, Reference Linnaeus1758), C. bicolor (Lamarck, Reference Lamarck1819), C. canaliculatus (Reeve, Reference Reeve1843), and C. ovalis (Reeve, Reference Reeve1843). The American species have a notch at the posterior margin and radial ribs with squamose nodes, while the European and Asian species have radial ribs with subrectangular nodes. Therefore, Huber’s (Reference Huber2010) hypothesis that American taxa could belong to distinct genera from European and Asian taxa could potentially be corroborated based upon morphological differences and distinct geographical distributions.

Cardites feruglioi (Petersen, Reference Petersen1946)

Figure 4.1–4.6

Figure 4

Cardites feruglioi (Petersen, Reference Petersen1946): (1) internal view of left valve, syntype SGN 9381, from Puesto Crettón; (2) external view of left valve, syntype SGN 9381, from Puesto Crettón; (3) external view of right valve, syntype SGN 9379, from Puesto Crettón; (4) internal view of right valve, syntype SGN 9379, from Puesto Crettón; (5) external view of right valve, MACN-Pi 5763, from Cerro Tiltilco; (6) internal view of right valve, MACN-Pi 5763, from Cerro Tiltilco. Scale bar represents 10 mm.

1946 Venericardia feruglioi Reference PetersenPetersen, p. 126, pl. 10, figs. 3–5.

1990 Venericardia feruglioi Petersen; Reference Medina, Camacho and MalagninoMedina et al., p. 140, pl. 1, figs. 1–3.

1992 Venericardia feruglioi Petersen; Reference CamachoCamacho, p. 37.

Type specimens

Syntypes SGN 9379 and SGN 9381. One right and one left valve, from Puesto Crettón, (Chubut Province).

Diagnosis

Shell subtriangular to subrectangular outline, with sinuous ventral margin. Lunule small. Left anterior tooth small and triangular; right middle tooth very curved, broad, and prominent. Radial ribs (28–29) with elongated rectangular nodes, better developed on ventral and posterior regions of valves than elsewhere, and with reduced intercostal spaces.

Occurrence

General Roca and Coli Toro Plateau areas (Danian, Roca Formation, Río Negro Province), and Puesto Crettón (Danian, Lefipán Formation, Chubut Province).

Description

Shell medium-sized, thick, triangular to subrectangular; anterior margin rounded, ventral margin sinuous, posterior margin truncated with right angle between it and ventral one, dorsal margin inclined, slightly convex; posterior area defined by convexity change starting from seventh or eighth radial rib. Umbones large, recurved, placed near anterior third of valve length. Lunule very small. Hinge of right valve high, with sinuous ventral edge below middle tooth; anterior tooth absent; middle tooth large, high, strongly curved, inclined backwards, with broad base, dorsal tip sharp; fine striations on dorsal surface; posterior tooth long, thin, curved.

Hinge of left valve high, with straight ventral edge; anterior tooth short, triangular, inclined backwards, with straight anterior and curved posterior edges; posterior tooth long, curved, higher than anterior one. External sculpture of 28–29 broad, low radial ribs of subrectangular transverse section, covered with obsolete and elongated rectangular nodes, more strongly developed on ventral and posterior regions of valve; intercostal spaces reduced, with ‘V’-shaped transverse section; posterior area covered with seven or eight lower, narrower radial ribs. Pallial line at about one-quarter of valve height. Inner ventral margin with strong crenulations that are rectangular, truncated, and extend around margin until junction of ventral and posterior margins.

Remarks

Petersen (Reference Petersen1946) erected C. feruglioi based on a large number of shells collected from the Danian section of the Lefipán Formation, exposed in the middle Chubut River area (Chubut Province). Later, Rodríguez et al. (Reference Rodríguez, Getino and Sepúlveda1995) assigned a left valve (CPBA 17276) to this species from Cerro Tiltilco (Roca Formation, Río Negro Province). This specimen does not resemble the specimens in Petersen (Reference Petersen1946), therefore we included it in the new species. The description of C. feruglioi is expanded here to include new specimens from Puesto Nahuel Cheo, Puesto Carmelo Ibañez, and unspecified fossiliferous sections describe by R. Wichmann at Bajo Lenza Niyeu and Bajos Hondos. Petersen (Reference Petersen1946) assigned this species to Venericardia, but that genus has subquadrate shells, strongly truncated posterior margin, and paracostal ribs sculptured with rounded nodes. The presence in C. feruglioi of subtriangular shells, radial ribs covered with subrectangular nodes, without paracostal ribs, and the absence of a right anterior tooth place this species within Cardites Link, Reference Link1807.

Cardites feruglioi differs from C. antiquatus (Linnaeus, Reference Linnaeus1758) (Chavan, Reference Chavan1969, fig. E56.1) by its larger shells with subtriangular outlines, a sinuous ventral margin, shorter left anterior and wider right middle teeth, and a greater number of radial ribs that are more strongly developed on the ventral and posterior regions of the valves.

Cardites canaliculatus (Reeve, Reference Reeve1843), C. bicolor (Lamarck, Reference Lamarck1819) (Recent, Indian Ocean), and other subtriangular species from Europe and Asia (Huber, Reference Huber2010, p. 251–252) can all be distinguished from C. feruglioi by having a larger lunule and sculpture with fewer radial ribs.

Cardites floridanus (Conrad, Reference Conrad1838) (Recent, from North Carolina, USA to Northern Brazil) and the remaining elongate American species (Huber, Reference Huber2010, p. 251–252) differ from C. feruglioi by their elongate outlines, with more rounded umbones and large lunules.

Cardites feruglioi can be distinguished from C. partschii (Goldfuss, Reference Goldfuss1840) (Miocene from Europe; Sieber, Reference Sieber1954, pl. 1, fig. 3) by having a larger shell with subtriangular outlines, and narrower radial ribs that become better developed on the ventral and posterior regions of the valves and are separated by wider intercostal spaces.

Genus Kalelia new genus

Type species

Cardita multicostata Lamarck, Reference Lamarck1806. Late Paleocene, Paris Basin, France.

Included species

K. burmeisteri (Böhm, Reference Böhm1903), K. pectuncularis (Lamarck, Reference Lamarck1806).

Diagnosis

Carditid with large shells for the family, thick and subcircular. Posterior margin convex, large umbones and posterior area defined by an umbonal carina and a convexity change. Lunule large, vertically oriented. Hinge high, with wide ventral development. Right anterior tooth long, inclined backwards; right middle tooth thick, strongly curved, with broad base. Left anterior tooth triangular, very broad, inclined backwards, with very convex posterior edge. External sculpture of tripartited radial ribs, 25–30 wide, most prominent on anterior, intercostals spaces confined to a narrow groove.

Etymology

The name honors Kal-El, Kryptonian name of Superman, the first superhero in comic books. This genus is one of the oldest and largest alticostate carditids.

Remarks

Kalelia n. gen. is the largest member of all alticostate carditids, with shells reaching up to 60 mm in height. It is characterized by the development of a tall hinge plate, prominent teeth, a large lunule, and the presence of low radial ribs; subrectangular in cross section. These characters are shared with planicostate carditids, but the development of tripartite radial ribs places Kalelia within alticostates carditids. Rutsch (Reference Rutsch1936) and McClure (Reference McClure2009) already mentioned the possibility that ‘Venericardia’ pectuncularis convergently developed some planicostate characters.

We proposed including in Kalelia n. gen., apart from the type species ‘Cardita’ multicostata (Lamarck, Reference Lamarck1806) (Cossmann and Pissarro, Reference Cossmann and Pissarro1904, pl. 31, fig. 97–3), the late Paleocene species ‘C.’ burmeisteri (Böhm, Reference Böhm1903) (Roca and Salamanca formations, early Danian, Argentina) (Fig. 5.1–5.11) and ‘C.’ pectuncularis (Lamarck, Reference Lamarck1806) (Cossmann and Pissarro, Reference Cossmann and Pissarro1904, pl. 31, fig. 97–2) (Fig. 6.1, 6.2), from the Sables de Bracheux, France. These species have large shells with strong hinge teeth and the particular external sculpture described above. The poorly known species ‘V.’ marylandica (Clark and Martin, Reference Clark and Martin1901) (Clark and Martin, Reference Clark and Martin1901, pl. 40, fig. 7; Nanjemoy Formation, early Eocene, USA) is possibly a North American representative of this genus.

Figure 5

Kalelia burmeisteri (Böhm, Reference Böhm1903) n. comb. (1–7): (1) external view of left valve, CPBA 8338, from Puesto Álvarez; (2) external view of left valve with shell removed, CPBA 8338, from Puesto Álvarez; (3) external view of right valve, CPBA 8338, from Puesto Álvarez; (4) internal view of right valve, MACN-Pi 5357, from General Roca; (5) left view of internal mold, CPBA 8338, from Puesto Álvarez; (6) left view of internal mold, holotype MLP 15294f, from General Roca; (7) left view of internal mold, holotype MLP 15294a, from General Roca. Kalelia multicostata (Lamarck, Reference Lamarck1806) n. comb. (8–11): (8) internal view of left valve, holotype MNHN A07711, from Abbecourt, France; (9) external view of left valve, holotype MNHN A07711, from Abbecourt, France; (10) internal view of right valve, MNHN F07559, from Noailles, France; (11) external view of right valve, MNHN F07559, from Noailles, France. Scale bar represents 10 mm.

Figure 6

Kalelia pectuncularis (Lamarck, Reference Lamarck1806) n. comb. (1, 2): (1) external view of right valve, holotype GMNH 46030, from Bracheaux, France; (2) internal view of right valve, holotype GMNH 46030, from Bracheaux, France. ‘Venericardia’ iheringi (Böhm, Reference Böhm1903) (3–5): (3) left view of internal mold, MLP 10220a, from Puesto Pircala; (4) right view of internal mold, syntype MLP 15294c, from General Roca; (5) left view of internal mold, syntype MLP 15294c, from General Roca. Scale bar represents 10 mm.

Kalelia n. gen. differs from Venericardia Lamarck, Reference Lamarck1801 (La Perna et al., Reference La Perna, Mandic and Harzhauser2017, fig. 3) in having larger shells with more nearly circular outlines, a convex posterior margin instead of a truncated one, a larger lunule, a higher hinge plate, a triangular right anterior tooth, and fewer radial ribs that are separated by intercostal spaces defined by narrow grooves.

Kalelia n. gen. can be distinguished from Arcturellina Chavan, Reference Chavan1951 (type species C. asperula Deshayes, Reference Deshayes1825, Eocene, Paris Basin) (Cossmann and Pissarro, Reference Cossmann and Pissarro1904, pl. 22, fig. 97-22) by having larger shells, convex posterior margin, higher hinge plate, long or straight right anterior tooth, triangular left anterior tooth, and fewer radial ribs covered with subcircular nodes instead of the subrectangular ones that characterize Arcturellina.

Kalelia n. gen. can be distinguished from Claibornicardia Stenzel and Krause, Reference Stenzel and Krause1957 (Heaslip, Reference Heaslip1968, pl. 26, figs. 6–11) because Kalelia has larger and more nearly circular shells, a higher and more robust hinge, and fewer, lower, and wide radial ribs.

Kalelia n. gen. can be separated from Rotundicardia Heaslip, Reference Heaslip1968 (Heaslip, Reference Heaslip1968, pl. 22, figs. 8–9, pl. 23, figs. 1–2) by having a rounded posterior margin, convex umbones, a well-developed posterior area, the presence of a lunule, the higher number of radial ribs with subcircular nodes, and narrower intercostals spaces separating the ribs.

Kalelia burmeisteri (Böhm, Reference Böhm1903) n. comb.

Figure 5.1–5.7

1902 Cardita morganiana Rathbun; Reference BurckhardtBurckhardt, p. 216, figs. 1,7.

1903 Cardita burmeisteri Reference BöhmBöhm, p. 72.

1903 Cardita Burckhardti Reference IheringIhering, p. 205.

1907 Venericardia burmeisteri (Böhm); Reference IheringIhering, p. 23.

1938b Venericardia burmeisteri (Böhm), ‘Forma B’; Reference Fossa ManciniFossa-Mancini, p. 263.

1967 Venericardia paleopatagonica var. australis Reference MasiukMasiuk, p. 243, pl. 5, fig. 2.

Type specimens

Holotype MLP 15294a and 15294f. Two internal molds from General Roca (Río Negro Province).

Diagnosis

Shell medium-sized, posterior margin slightly convex, dorsal margin sloping from beaks to posterior one, posterior area sculptured by three or four higher and wide radial ribs, continued by three lower and narrower other ones. Umbones subcentrally placed. External sculpture of 25 wide and low radial ribs.

Occurrence

General Roca area (early Danian, Roca Formation, Río Negro Province) and Puesto Álvarez (early Danian, Salamanca Formation, Chubut Province).

Description

Shell medium-sized, thick, subcircular in outline, with rounded anterior and ventral margins, weakly convex posterior margin, and curved dorsal margin with pronounced slope from beaks to posterior end; posterior area defined by convexity change starting from sixth or seventh radial rib. Umbones large, convex, near center of valves. Lunule large, convex, sunken, vertically oriented. Right valve hinge with straight ventral edge; anterior tooth thin, large, inclined backwards; middle tooth large, strongly curved, strongly inclined backwards, with broad base, higher towards dorsal extreme in lateral view; posterior tooth thin, curved, extending to center of middle tooth. Left hinge not seen. External sculpture of 25 wide, low, tripartite radial ribs, more prominent towards anterior region of valves, transverse section triangular in dorsal region but semicircular in central region; central radial ribs covered with nodes, subcircular transverse in cross section; paracostal ribs smooth, semicircular transverse in cross section, as wide as central radial rib; intercostal spaces, subquadrate transverse in cross section, each wider than one radial rib; posterior area sculptured with three or four higher, wider ribs, followed by three lower and narrower ones. Pallial line at about one-quarter of total valve height. Inner ventral margin with prominent crenulation; crenulations triangular, truncated, extending along entire margin to center of posterior adductor muscle scar.

Remarks

Internal molds studied by Burckhardt (Reference Burckhardt1902), Böhm (Reference Böhm1903), and Ihering (Reference Ihering1903, Reference Ihering1907) are characterized by their large size, subrounded outline, convex umbones, and particularly by the presence of a postero-ventral carina. The specimens collected by Masiuk (Reference Masiuk1967) and described as Venericardia paleopatagonica var. australis, include composite molds, with internal molds and valves that allowed us to identified Masiuk’s variety with K. burmeisteri. The carina present in the molds corresponds to the change in convexity and sculpture observed in the preserved valves.

Burckhardt (Reference Burckhardt1902) identified this species as Cardita morganiana Rathbun, Reference Rathbun1875, a Brazilian taxon from Maria Farinha (Paleocene) and Pirabas (Miocene) formations (Penna, Reference Penna1965; Tavora et al., Reference Tavora, Rodrigues Dos Santos and Araújo2010). The Brazilian species (White, Reference White1887, pl. 8, figs. 18–21) differs from K. burmeisteri in having smaller and more robust shells with umbones placed more anteriorly, and in having more pronounced tripartition and the ribs sculptured with squamose nodes.

Kalelia multicostata (Lamarck, Reference Lamarck1806) (Cossmann and Pissarro, Reference Cossmann and Pissarro1904, pl. 31, fig. 97–3; Sables de Bracheux) can be separated from K. burmeisteri by being larger, with a more horizontal dorsal margin, anteriorly placed umbones, the posterior area sculptured with radial ribs of equal width, and by having more numerous radial ribs with better-developed tripartition over center of the valves.

Kalelia burmeisteri is distinguished from K. pectuncularis (Lamarck, Reference Lamarck1806) (Chenu, Reference Chenu1842, pl. 2, fig. 8; Cossmann and Pissarro, Reference Cossmann and Pissarro1904, pl. 31, fig. 97–2; Sables de Bracheux) by its smaller size, sloping dorsal margin, subcentrally placed umbones, and fewer and wider radial ribs.

‘Cardita’ morganiana and ‘Cardita’ beaumonti

(Fig. 6.3; MLP 10220a–d). These two species have been mentioned frequently in the literature of the Paleocene from Argentina (Behrendsen, Reference Behrendsen1891; Burckhardt, Reference Burckhardt1900, Reference Burckhardt1902; Windhausen, Reference Windhausen1918, Reference Windhausen1931; Weaver, Reference Weaver1927, Reference Weaver1931; Gerth, Reference Gerth1935; Fossa Mancini, Reference Fossa Mancini1938a, Reference Fossa Mancini1938b).

As stated above, ‘Cardita’ morganiana Rathbun, Reference Rathbun1875 is a Cenozoic Brazilian species that is possibly related to Baluchicardia Rutsch and Schenck, Reference Rutsch and Schenck1943. ‘Cardita’ morganiana was cited for the first time in Argentina from Puesto Pircala (Malargüe, Roca Formation, Mendoza Province) (Behrendsen, Reference Behrendsen1891), based on internal molds. These outcrops were assigned a Maastrichtian age by Parras et al. (Reference Parras, Casadío and Candela1998). Burckhardt (Reference Burckhardt1902) indicated the presence of ‘C.’ morganiana in the type area of the Roca Formation, which is of early Danian age according to del Río et al. (Reference del Río, Concheyro and Martínez2011).

Weaver (Reference Weaver1927, Reference Weaver1931) mentioned the presence of ‘Cardita’ beaumonti (=Baluchicardia beaumonti) in General Roca rocks. Baluchicardia beaumonti comes from Maastrichtian and Danian beds of northwestern India and Pakistan (Calcaire jaune de la chaine d’Hala, Sind Region), and North Africa (d’Archiac and Haime, Reference D’Archiac and Haime1854; Rutsch, Reference Rutsch1936; Heaslip, Reference Heaslip1968). According to Fossa Mancini (Reference Fossa Mancini1938a), this species was mistakenly mentioned by Weaver (Reference Weaver1927) because the author followed the ideas of Fritzsche (Reference Fritzsche1919), who synonymized ‘C.’ morganiana with ‘C.’ beaumonti. Fossa Mancini (Reference Fossa Mancini1938a) concluded that this synonymy is invalid.

The specimens from the area of General Roca (MLP 15294a–f) were used for erecting the species ‘C.’ burmeisteri (=Kalelia burmeisteri) and ‘C.’ iheringi (both discussed below) by Böhm (Reference Böhm1903).

The only specimens found in Puesto Pircala, Malargüe (‘Cardita’ morganiana of Behrendsen, Reference Behrendsen1891 and Burckhardt, Reference Burckhardt1900) are small internal molds (MLP 10220a–d) with triangular outlines and very rounded margins. The absence of internal characters prevents generic and specific assignment. Casadío (Reference Casadío1994) considered them to be juveniles of Venericardia ameghinorum (Ihering, Reference Ihering1907), but Parras et al. (Reference Parras, Casadío and Candela1998) placed them in V. iheringi (Böhm, Reference Böhm1903). Venericardia iheringi is another species based on internal molds, and the Malargüe casts are very similar to this species. In this paper we accept the assignment by Parras et al. (Reference Parras, Casadío and Candela1998), and assign the specimens MLP 10220a–c to ‘Venericardia’ iheringi.

In this way and according to Fossa Mancini’ (Reference Fossa Mancini1938b), the presence of ‘Cardita’ morganiana and ‘C.’ beaumonti in Argentina is rejected.

‘Venericardia’ iheringi (Böhm, Reference Böhm1903 )

(Fig. 6.4, 6.5; MLP 15294b-e [Syntypes]; MLP 4298, 5377, 5387, 5517, 5125, 7625, 8866, 8955, 9455, 9726, 10506; MACN-Pi 356; CPBA 6405, 6408; MHNSR:Pi 1010, 1385, 1386, MACN-Pi 5750, MACN-Pi 5754, MACN-Pi 5749, MACN-Pi 5745). As in the previous case, this species was erected by Böhm (Reference Böhm1903) based on the internal molds described by Burckhardt (Reference Burckhardt1902, p. 219, figs. 2–6) from General Roca (Danian, Roca Formation). Ihering (Reference Ihering1907) included it within Venericardia, but this assignment is not confirmed because this species lacks hinge and external sculpture, the most valuable characters required for a more precise generic placement among carditids. ‘Venericardia’ iheringi has small to medium-sized shells with subtriangular to subquadrate outlines, rounded margins, prominent and very convex umbones placed subcentrally, and 21–22 radial ribs that are wider than their intercostals spaces. It is distinguished from casts of Kalelia burmeisteri (Böhm, Reference Böhm1903) by its smaller size with more rounded margins and by the absence of an umbonal-ventral carina. None of the other species from Roca Formation has the set of characters present in ‘V.’ iheringi. Ihering (Reference Ihering1907) mentioned a variation of this species, which he named Venericardia iheringi var. boehmi, with a more subquadrate outline, but it is difficult to differentiate from other specimens. Therefore, ‘Venericardia’ iheringi is a species with uncertain affinities and we cannot assign it to any of the other species described from the Roca Formation.

Venericardia ameghinorum (Ihering, Reference Ihering1907 )

(MACN-Pi 340 [Holotype], 5213; CPBA 6406, 6409, 6410, 6412; MLP 5006, 6315, 7285, 7737, 8951, 8956, 10503, 10504, 10505; MHNSR:Pi 1398). Venericardia ameghinorum was erected by Ihering (Reference Ihering1907) based on internal molds from General Roca (Roca Formation). This species has elongated shells that are easily distinguishable from other Paleocene carditid species. The elongate outlines with a sinuous ventral margin, and strongly recurved and separated orthogyrous umbones, placed this species within the genus Arca Linnaeus, Reference Linnaeus1758 (family Arcidae), as already mentioned by del Río et al. (Reference del Río, Concheyro and Martínez2011).

cf. ‘Cyclocardia’ sp. (del Río et al., Reference del Río, Martínez, Stilwell and Concheyro2007)

(GHUNLPam 22888, 22897–22900). Del Río et al. (Reference del Río, Martínez, Stilwell and Concheyro2007) described cf. Cyclocardia sp. from the Roca Formation in Cerros Bayos (Danian, La Pampa Province), based on four internal molds of articulated individuals. The specimens GHUNLPam 22888 and 22898 have elongate outlines, strongly recurved umbones, and slightly sinuous ventral margin, which placed them within Arca ameghinorum (Ihering, Reference Ihering1907).

The specimens GHUNLPam 22897 and 22899 have more circular outlines, rounded margins, subcentrally placed umbones, and at least 20 radial ribs. Del Río et al. (Reference del Río, Martínez, Stilwell and Concheyro2007) assigned them tentatively to Cyclocardia Conrad Reference Conrad1867 because of the number of radial ribs and the subcircular outline. ‘Venericardia’ iheringi Ihering, Reference Ihering1907 has a similar shape, but a less rounded margin, and an identical number of radial ribs. Here, these specimens are placed tentatively with ‘V.’ iheringi.