Procardium diluvianum ( 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 : 734-737

Procardium diluvianum ( Lamarck, 1819)

Figs. 3 , 4 .

1814 Cardium hians sp. nov.; Brocchi 1814: 508, pl. 13: 6 (non C. hians Lightfoot, 1786 [nomen nudum], nec Spengler, 1799).

1819 Cardium diluvianum sp. nov.; Lamarck 1819: 18.

1908 Cardium (Ringicardium) hians var. rotundata ; Cerulli Irelli 1908: 24, pl. 4: 7 (non Cardium rotundatum Carpenter, 1857 ).

1952 Cardium hians Brocchi, 1814 ; Rossi Ronchetti 1952: 73–75, fig. 28a–d.

2004 Cardium diluvianum Lamarck, 1819 ; Hylleberg 2004: 920, unnumbered figure.

2014 Cardium paleobrocchii ; Hylleberg 2014: 43, figs. 8, 9B (nomen novum for C. hians Brocchi, 1814 ).

Material. — Syntype of Cardium hians Brocchi, 1814 , MSNM i13317, one shell from Pliocene , northern Italy . Holotype of Cardium diluvianum Lamarck, 1819 , MNHN. F.A50147 one valve from Pliocene, Siena, Italy. MRSN BS.131.03.001, two valves, MRSN BS.131.03.001/02, one valve, MRSN BS.131.03.001/03, three valves; from Pliocene , Asti Hills , Italy; MRSN BS.131.03.001/01, one valve from Pliocene , Masserano , Italy. MPUR no registration number (unnumbered Cerulli Irelli collection), one valve from Early Pleistocene , Farnesina , Italy. NHMW1836. XII.895, two fragments of one valve, NHMW 1862.II.22, one shell; from Pliocene, Castell’Arquato, Italy. NHMW 1855.I.618, one valve, NHMW1855.I.619, one valve, NHMW 1855.I.620, one valve, from Early Pleistocene, Monte Mario, Italy. NHMW1877.XVIII.115, one valve from Pliocene, Valle Andona, Italy. NHMW1853.XXXVI.32, one valve, NHMW 1852.XXXII.143a, one valve, from Pliocene, Rhodes, Greece. RGM.794093 (van Nieulande collection), one valve, JJTP3383 , one valve (nine fragments), JJTP2073 , two valves, JJTP1001 , two fragments, PH 42439, three valves; from Zanclean (Pliocene), Bonares, Spain. RGM.48583 (van Nieulande collection), one valve, RGM.794096 (van Nieulande collection), one shell, RGM.48582 (van Nieulande collection), one shell (one valve), JJTP1657 , one fragment, PH 40489, one valve; from Piacenzian (Pliocene), Castell’Arquato, Italy. RGM.794097 (van Nieulande collection), one valve, RGM.794101 (van Nieulande collection), one valve; from Pliocene, Siena, Italy. USNM 82258, one valve from Pliocene, Asti, Italy. JJTP4736 , one valve from Pliocene, Castelfiorentino, Italy. MPUB2017/1A, ca. 30 fragments from Early Pleistocene, Gravina in Puglia, Italy. MPUB 2017/1B, four valves from Pliocene, Cerignola, Italy. MNHN F.A50669, one fragment from Zanclean (Pliocene), Pichegu, France. EK uncatalogued specimen, two valves from Pliocene, Tétouan, Morocco. PH 40632, one valve from Pliocene, Belveglio, Italy. JV uncatalogued specimen, one valve from Piacenzian (Pliocene), Montezago, Italy .

Description.— Shell large (L up to 125 mm), slightly longer than 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 17–21 primary radial ribs, on anterior half each interspace with a weakly defined, rather broad secondary riblet. Median primary ribs sharply delimited, broad, high rounded and about as wide as interspaces. Anterior ribs prominent with conical, ventrally hollow scales, placed on rib top. Cross-section of anterior and median ribs trapezium-shaped, with a radial groove on rib tops. Ribs on postero-medial slope asymmetrical in cross section, ultimately flattened posteriorly, with sculpture on posterior rib flanks gradually developing into 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.

Remarks.— Cardium hians Brocchi, 1814 is a primary junior homonym of C. hians Spengler, 1799 ( Lamy 1941; Smith 1945; Fischer-Piette 1977; Hylleberg 2004), the latter being an objective junior synonym of Fulvia aperta (Bruguière, 1789) by selection of the same specimen as lectotype for both taxa ( Vidal 1994). The next available name, which has been mostly disregarded in the literature, is Cardium diluvianum Lamarck, 1819 .

The description of C. diluvianum by Lamarck (1819: 18) was based on a fossil from Siena (Tuscany) collected by Georges Cuvier. To the short description “C. testâ cordatâ, antice angulatâ; costis 14, distantibus, convexis; vulvâ elevatâ, subcarinatâ”, Lamarck (1819) added the size of 80 mm. Unfortunately, the holotype, first illustrated by Hylleberg (2004: 920, unnumbered figure), is a poorly preserved left valve ( Fig. 3B ), apparently with at least 17–18 ribs.

Brocchi (1814: 508, pl. 13: 6) described C. hians from the areas of Piacenza, Siena and Asti, northern Italy, with the following diagnosis: “Testa subcordata tumida, costis 17 distantibus, antice depressis, aculeatis, postice tuberculis raris cochleariformibus instructis, valvis anterius hiantibus, margine hiatus profundissime serrato”. The figured syntype of C. hians , redescribed by Rossi Ronchetti (1952: 73–75, figs. 28a–d) who erroneously regarded it as the holotype, is an articulated shell bearing 17 ribs on the left valve and 18 on the right one ( Fig. 3A ).

The synonymy between C. hians and C. diluvianum is based on the following considerations: (i) both types share a comparable size, rib morphology and number of ribs; (ii) both species were described from fine-grained deposits of Pliocene age, usually referred to as Argille Subappennine, widely cropping out in northern Italy. Study material and literature data ( de Stefani 1874; de Stefani and Pantanelli 1879; Chirli 2016: 66, pl. 12: 1–4) confirm the occurrence of this large cardiid in the area of Siena, in Zanclean-Piacenzian deposits ( Bossio et al. 2002).

The confusion between this fossil species and the living one was initiated by Lamarck (1819: 4), who suggested that the latter might appear to be the “analogue vivant” of C. hians . Consequently, Lamarck et al. (1835: 390, footnote) regarded C. indicum as a junior synonym of C. hians , an opinion followed by many subsequent authors ( Petit 1840; Weinkauff 1862; Smith 1945; Ghisotti 1971; Van Aartsen and Giannuzzi Savelli 1991; etc.). Recently, Hylleberg (2014) reported slight morphometric differences between C. hians and C. indicum , in addition to the occurrence of spines on the postero-dorsal margin in the fossil species. He thus kept C. hians distinct from the living species, proposing the replacement name C. paleobrocchii for the former.

Indeed, the fossil species and the living one are here considered distinct, Cardium paleobrocchii being therefore another synonym of Procardium diluvianum , but the differences between the two species are mostly represented by sculpture ( Table 2). The living species has a range of 20–24 ribs vs. 17–21 in P. diluvianum ; the scales on the anterior slope of P. diluvianum are markedly funnell-shaped or broadly horseshoe-shaped ( Figs. 4B , 16G ), whereas they are more erect and rectangular, shingle-shaped in P. indicum ( Figs. 1F , 16H ). In addition, the radial ribs of P. diluvianum are broader, more pronounced and sharply delimited ( Fig. 16G ) and the secondary riblets are very weakly developed ( Figs. 4A 3 , 16G ), whereas in P. indicum the radial ribs are poorly delimited and the secondary riblets are more distinct ( Figs. 1F , 16H ). Up to five spines can be present on the postero-dorsal margin of P. diluvianum , as observed by Hylleberg (2014), but this character is variable, spines being distinct to almost absent. No appreciable differences in the hinge occur between the two species. The maximum recorded size is 125 mm in P. diluvianum , as can be extrapolated from Brambilla (1976: pl. 28: 2), while P. indicum is smaller ( Table 2).

Some variability, apparently unrelated to stratigraphic or geographic distribution, is observed with regard to the strength of the radial sculpture (e.g., Fig. 4A 2, D 2 ), with rare cases of unusually wide and strong ribs ( Fig. 3G ). Cerulli Irelli (1908: 24, pl. 4: 7) proposed Cardium (Ringicardium) hians var. rotundata , with more equilateral and equidimensional shell, the posterior margin not sloping, and 17–18 ribs, instead of 19–20, based on Calabrian (Early Pleistocene) material from Rome. The single valve present in the Cerulli Irelli collection ( Fig. 3C ) is similar to that illustrated as C. (R.) hians var. rotundata and provides no evidence for keeping it distinct. C. (R.) hians var. rotundata is therefore included in the synonymy of P. diluvianum .

All records of C. hians from the Miocene of Europe were based on misidentifications. Conversely, all records those from the Pliocene and Pleistocene of Italy ( Sacco 1899: 42, pl. 10: 11–13; Cerulli Irelli 1908: 24, pl. 4: 5–7; Gignoux 1913; Pavia and Demagistris 1971: 99, pl. 3: 1; Brambilla 1976: p. 110, pl. 28: 2; Chirli 2016: 66, pl. 12: 1–4), the Pliocene of southern France ( Fontannes 1882: 80, pl. 5: 1; Chirli and Richard 2008: 96, pl. 21: 6), southern Spain ( Andrés 1987: 112, pl. 3: 1, 2), Greece ( Syrides 1995) and Cyprus ( Moshkovitz 2012), should be referred to P. diluvianum . The studied material is representative of this distribution and also includes the early Pliocene of Tétouan, at the Mediterranean side of northern Morocco.

Stratigraphic and geographic range. —In the early Pliocene–Early Pleistocene interval, P. diluvianum occurred from the Atlantic Guadalquivir Basin in southern Spain to the eastern Mediterranean. Most probably, it also ranged further to south, along the coast of West Africa, similarly to the modern distribution of P. indicum .

Figures

Fig. 3. Cardiid bivalve Procardium diluvianum (Lamarck, 1819). A. Syntype of Cardium hians Brocchi, 1814, MSNM i13317, Pliocene, northern Italy (photo Giorgio Teruzzi); external (A1) and umbonal (A2) views. B. Holotype of Cardium diluvianum Lamarck, 1819, MNHN.F.A50147, Pliocene, surroundings of Siena, Italy; external view (photo Jacques Mouchart, http://coldb.mnhn.fr/catalognumber/mnhn/f/a50147). C. MPUR no registration number (unnumbered Cerulli Irelli collection), Early Pleistocene, Farnesina, Italy; external view. D. RGM.794093 (van Nieulande collection), Zanclean (Pliocene), Bonares, Spain; external view. E. RGM.48582.a, Piacenzian (Pliocene), Castell’Arquato, Italy; umbonal view. F. MRSN BS.131.03.001, Pliocene, Asti Hills, Italy; external view. G. RGM.48583, Piacenzian (Pliocene), Castell’Arquato, Italy; external view. Scale bar 50 mm.

Fig. 4. Cardiid bivalve Procardium diluvianum (Lamarck, 1819) from Italy. A. MPUB 2017/1B, Pliocene, Cerignola; internal (A1) and external (A2) views, detail of sculpture (A3). B. MPUB 2017/1A, Pliocene, Cerignola; detail of anterior sculpture. C. MPUB 2017/1A, Early Pleistocene, Gravina in Puglia; detail of posterior spines (inner view). D. PH 40489, Piacenzian (Pliocene), Castell’Arquato; internal (D1) and external (D2) views. Scale bars: A1, A2, D1, D2, 50 mm; A3, 10 mm; B, C, 5 mm.

Fig. 16. Comparative rib cross-sections and rib sculpture for species of Procardium. Schematic drawings based on the third/fourth rib anterior to the midline, close to the margin of an adult shell. A. P. magnei sp. nov. B. P. jansseni sp. nov. (upper part of rib sculpure reconstructed). C. P. danubianum (rib sculpture undefined). D. P. kunstleri. E. P. aff. kunstleri. F. P. avisanense. G. P. diluvianum. H. P. indicum. Median rib, showing radial groove on rib top (H2). Note presence of microscopic granulations (white arrow) and secondary riblet in interspace (black arrow). Scale bar 5 mm.

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.