Procardium indicum ( Lamarck, 1819 )

Poorten, Jan Johan Ter & Perna, Rafael La, 2017, The West African enigma: Systematics, evolution, and palaeobiogeography of cardiid bivalve Procardium, Acta Palaeontologica Polonica 62 (4), pp. 729-757 : 732-734

Procardium indicum ( Lamarck, 1819)

Figs. 1 , 2A .

1819 Cardium indicum sp. nov.; Lamarck 1819: 4.

1844 Cardium hians Brocchi, 1814 ; Reeve 1844: pl. 5: 27 (non C. hians Brocchi, 1814 ).

1866 Cardium darwini ; Mayer 1866: 69–71 (nomen novum for C. indicum Lamarck, 1819 ).

1950 Ringicardium schoelleri ; Magne 1950: 123 (nomen novum for C. darwini Mayer, 1866 ).

1964 Cardium delpeutum sp. nov.; McGill 1964: 4, unnumbered figure.

1977 Cardium (Cardium s.s.) indicum Lamarck, 1819 ; Fischer-Piette 1977: 112, pl. 10: 4a, b.

2004 Cardium indicum Lamarck, 1819 ; Hylleberg 2004: 843, unnumbered figures.

Material. — Holotype of Cardium indicum Lamarck, 1819 , MNHN-IM-2000-25143, one valve from “l’Ocean des grandes Indes” [= Indian Ocean: erroneous]. ZMA.MOLL. 3318, two valves from Algier, Algeria. ZMA.MOLL.210347 (Hessel collection), two shells from Agadir, Morocco. RMNH.MOL. 119659 (alive), one shell from Atlantic Ocean (depth 38–41 m), Banc d’Arguin, Mauritania. RMNH.5006726 (ter Poorten collection), one shell from Algeria. JJTP3288 , one shell from Mediterranean Sea (dredged 300–380 m), Cherchell, Algeria. JJTP1923 , one valve from Agadir, Morocco (from fishermen). JJTP3442 , one shell, JJTP45 , one shell, from Senegal. JJTP 2075 , one shell from Dakar, Senegal. JJTP443 , one shell from Mbour, Senegal. All Recent material.

Description.— Shelllarge(L 75–115mm),slightlylongerthan high, almost equilateral, relatively thin, inflated, moderately gaping posteriorly. Umbo slightly prosogyrate. Anterior and ventral margins rounded, posterior margin truncated and nearly straight. Shell bearing 20–24 primary radial ribs, on anterior half each interspace with a rather well defined, thin secondary riblet. Median primary ribs weakly delimited, rather broad, low rounded to weakly triangular and about as wide as interspaces. Anterior ribs prominent with roof tile-shaped, ventrally hollow scales, placed on rib top. Cross-section of anterior and median ribs trapezium-shaped, with a radial groove on the rib tops. Ribs on postero-medial slope asymmetrical in cross section, ultimately flattened posteriorly, with sculpture on posterior rib flanks gradually developing into close-set, pointed, posteriorly directed spines. Rib impressions clearly visible from within. Hinge plate rather narrow and slightly sinuous, hinge angle very large. Hinge and ligament: as for genus. Lunule not well defined, dorsal margin slightly raised anterior of umbo. Exterior colour dirty white, with commarginally arranged brownish areas, posteriorly pink or purple, except for white spines. Rusty-brown deposit present on interspaces of postero-medial part. Interior colour white with traces of cream, posterior margin purple.

Remarks. —As remarked by some authors (e.g., Mayer 1866; Fischer-Piette 1977; Hylleberg 2004), Cardium indicum is not from the Indian Ocean, in spite of the original mention of “l’Ocean des grandes Indes” by Lamarck (1819). The type material (MNHN-IM-2000-25413), a left valve illustrated by Fischer-Piette (1977: pl. 10: 4a, b) and Hylleberg (2004: 843, unnumbered figures), should be considered as holotype because Lamarck (1819) mentioned the presence of only one valve in his description.

Mayer (1866: 69–71), explicitly referring to the citation of C. indicum by Lamarck (1819: 18), Lamarck et al. (1835: 390, footnote) and to the figure of C. hians by Reeve (1844: pl. 5: 27), proposed Cardium darwini as a replacement name for C. indicum , because of the wrong specific attribute used by Lamarck (“Le nom de C. indicum impliquant une contre-vérité, les règles de la nomenclature […] m’ont obligé a changer cette dénomination”). As further discussed, the description of C. darwini was based on a distinct Miocene species, mistaken by Mayer (1866) for the living C. indicum , most probably due to the inaccurate, somewhat misleading illustration of the Recent species by Reeve (1844). However, C. darwini remains nominally a synonym of C. indicum ICZN 1999 : Art. 72.7). Cardium delpeutum McGill, 1964 , described from off Luanda, Angola is another synonym of P. indicum ( Ghisotti 1974) .

Stratigraphic and geographic range.— Procardium indicum is essentially a tropical West African species, whose distribution ranges from Angola to Morocco, with a few deep water records from Tunisia and Algeria, in the westernmost Mediterranean ( Ghisotti 1971; Fischer-Piette 1977; Delongueville and Scaillet 2011; Dailianis et al. 2016). A Canary Islands record ( Gómez Rodríguez and Pérez Sánchez 1997) is based on a sole valve found in material dredged for artificial beach construction and needs confirmation. The species is mostly trawled or dredged, with deep water records up to 300– 380 m. The only examined live taken specimen is from 38–41 m, collected from muddy sand in Mauritania.

Some old records from other Mediterranean areas (e.g., Toulon, Naples, Corinth) were discussed by Ghisotti (1971) and Fischer-Piette (1977). If not based on misidentified reworked fossil shells (admittedly unlikely, because of shell fragility), these records could represent the occurrence of scattered relict populations of P. indicum throughout the Mediterranean.

Figures

Fig. 1. Cardiid bivalve Procardium indicum (Lamarck, 1819), RMNH.5006725 (ter Poorten collection), Recent, Algeria.Articulated shell in internal (A, C), external (B, D), and umbonal (E) views, with detail of anterior sculpture (F). Scale bars: A–E, 50 mm; F, 20 mm.

Fig.2. Hinge region of the right valve of Cardiinae type species and a related “Cardium” species. A. Procardium indicum (Lamarck, 1819), RMNH.5006726 ter Poorten collection), Recent, Algeria. B. Cardium costatum Linnaeus, 1758, RMNH.5006725 (ter Poorten collection), Recent, Angola. C. Bucardium ringens (Bruguière, 1789), RMNH.5006724 (ter Poorten collection), Recent, Senegal. D. “Cardium” burdigalinum (Lamarck, 1819), RGM.1309989 (ter Poorten collection), France, Léognan, Le Coquillat, early Miocene. Solid circles and ovals indicating positions of the tips of the teeth (A2–D2) and the positions and shapes of the cardinal teeth of the opposite valve (A1–D1). Note extremely hollowed anterior lateral socket in Procardium gen. nov. (1), angular antero-dorsal margin in Cardium (2), largely fused cardinals (3), strongly protuberant posterior ribs in Bucardium (4), and anterior and posterior ventral lateral teeth about equidistant from cardinals in “Cardium” (5). Scale bars 10 mm.