Procardium magnei, Poorten & Perna, 2017

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 : 749-752

Procardium magnei sp. nov.

Fig. 15 .

1866 Cardium darwini ; Mayer 1866: 69 (partim).

1912 Cardium (Ringicardium) darwini Mayer, 1866 ; Cossmann and Peyrot 1912: 492, pl. 21: 26, 27 (non C. darwini Mayer, 1866 ).

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

1994 Cardium (Ringicardium) darwini Mayer, 1865 (sic!); Marcomini 1994: 15.

Etymology: After André Magne, paleontologist and malacologist from the geological department of the Faculty of Sciences at the University of Bordeaux in the 1940s–60s, who first tried to settle the nomenclature of this species.

Type material: Holotype PH 11708, right valve (L 92 mm, H 86 mm) . Paratypes: PH 63240, left valve (L 68 mm, H ~ 57 mm), RGM.794098, right valve (L 76 mm, H 71 mm) from the type locality .

Type horizon: Yellow shelly sands, early Burdigalian, Miocene.

Type locality: Saucats “La Coquillière” (also known as “ Coquilleyre ”), Gironde department, France .

Material. —RGM.794100, one valve, PH 63241, two fragments, from early Burdigalian (Miocene), Saucats “La Coquillière”, France. JJTP4779, JJTP4780, three fragments from early Burdigalian (Miocene), Léognan “Le Coquillat”, France.

Diagnosis. —A rather large, inflated Procardium species with 18–19 sharply delimited high triangular flat-topped radial ribs. Scales rather well spaced and also covering the upper part of the rib flanks. Interspaces broad with variably developed minute granulations on anterior and median zones.

Description. —Shell large (L up to 92 mm), slightly longer than high, weakly inequilateral, relatively thin, inflated, with a moderately wide posterior gape, covering two-thirds of posterior margin length. Umbo slightly prosogyrate. Anterior and ventral margins rounded, postero-ventral margin rather angular, posterior margin truncated and nearly straight. Shell bearing 18–19 sharply delimited primary radial ribs, on anterior half alternating with a very weakly developed, broad and flattened secondary riblet. On median part, interspaces about 3–4 times wider than primary ribs. Anterior ribs high triangular, flat-topped with rather well spaced, broadly horseshoe shaped scales, also covering upper part of rib flanks and hollow ventrally. Ribs on postero-ventral slope becoming even more prominent high triangular, carrying slender shingle-shaped scales. Ribs ultimately flattened triangular on postero-dorsal slope and sculptured with pronounced spines, placed on posterior rib flanks, directed posteriorly. Fine commarginal growth lines present in interspaces, combined with a variably developed pattern of minute granulations on anterior and median zones. Rib impressions well visible from within, with notable deep incisions at postero-medial marginal zone. Hinge plate rather narrow, slightly sinuous; cardinal teeth nearly horizontally rotated. Left valve: two cardinal teeth of which the anterior one well defined, posterior one tiny; both teeth connected at their bases, with a deep socket below. Right valve: two similar sized, erect, pointed cardinal teeth, not touching at their bases but separated by a deep socket. Anterior lateral sockets curved and extremely excavated, lateral teeth of both valves thin, blade like. Tips of lateral teeth about equidistant from anterior cardinal. Ligament short. Lunule not well defined, dorsal margin slightly raised anterior of umbo.

Remarks. —Because of the incorrect usage of Mayer’s (1866) name by Cossmann and Peyrot (1912), Magne (1950) proposed Cardium schoelleri as a nomen novum ( ICZN 1999: Art. 72.7), evidently with the aim of giving a name to the fossil species from the Aquitaine Basin reported by Cossmann and Peyrot (1912). However, as a replacement name of C. darwini Mayer, 1866 , C. schoelleri is a synonym of C. indicum , while C. darwini sensu Cossmann and Peyrot (1912) remained an undescribed species.

Mayer (1866) referred some fossil cardiids from the Aquitaine Basin (Léognan, Saucats, Saint-Paul-lès-Dax, Saubrigues, Saint-Jean-de-Marsaq), from “Helvetian” localities in Switzerland, as discussed under P. danubianum , and from the Miocene and Pliocene of Algeria, to C. darwini . Evidently, as remarked by Cossmann and Peyrot (1912) and by Magne (1950), Mayer’s (1866) interpretation of C. darwini included more than one species. However, after Mayer’s (1866) description, the identity of the species on which he based his description is clear: it is the same as that reported from Léognan as C. (Ringicardium) darwini by Cossmann and Peyrot (1912: 492, pl. 21: 26, 27), who gave a more detailed description, including the hinge.

The main sculptural characters of Procardium magnei sp. nov. were clearly outlined by Mayer (1866: 70): 15–18 wide spaced ribs, thin, elevated and markedly sharp “distantes, très-minces, élevées et assez aiguës”. Scales, mostly worn out, are U- or V-shaped, straddling the ribs, as Mayer (1866: 70) tried to describe “côtes en forme de lamelles, qu’embrassent, pour ainsi dire, les écailles en cornets qui les surmontent” ( Fig. 16A ).

Types and the scarce additional material are from the early Burdigalian of the area of Saucats in the Aquitaine Basin. Geographic and stratigraphic details on these deposits were given by Cahuzac and Janssen (2010). Cossmann and Peyrot (1912) reported the present species from Léognan, another classical locality in the Aquitaine Basin, of early Burdigalian age ( Poignant et al. 1997; Cahuzac and Janssen 2010); their figured specimen (Cossmann and Peyrot 1912: pl. 2: 26, 27) has been rediscovered and is deposited in the MNHN collection ( Marcomini 1994). The other localities mentioned by Mayer (1866) include deposits whose age ranges from the Aquitanian (Saint-Paul-lès-Dax) to the Langhian (Saubrigues), including the late Burdigalian (Saint-Jean-de-Marsaq) ( Cahuzac and Janssen 2010), which could imply the complete stratigraphic range of the species. The records from Switzerland by Mayer (1866), apparently based on internal moulds, are from the Upper Marine Molasse (middle Burdigalian). As discussed above, they were most probably misidentified, as also the records from the Neogene of Algeria.

Procardium magnei sp. nov. shares its main sculptural characters with P. jansseni sp. nov., P. danubianum and in part with P. kunstleri ( Table 2). All of them have thin median ribs, triangular in cross-section, markedly different from the broad, convex ribs with a central groove of P. indicum , P. diluvianum , and P. avisanense . However, P. magnei sp. nov. is more similar in sculpture to P. jansseni sp. nov. than to the others: both species have sharply delimited radial ribs and weak secondary riblets ( Fig. 16A, B ), while in P. danubianum ( Fig. 16C ) the main ribs are not well delimited and the secondary riblets are more distinct. The rib separating the ventral and posterior slope is high triangular in P. magnei sp. nov., whereas it is thin and small in P. jansseni sp. nov. The scaly sculpture is not markedly variable among the Procardium species, but in P. jansseni sp. nov. the funnel-shaped scales wrap totally the rib ( Figs. 13B, E 1 , G, 16B ). Similar scales are also present in P. magnei sp. nov., but less markedly and mainly on the anterior ribs ( Figs. 15A 4 , C 2 , 16A ), while the scaly sculpture is poorly

C

preserved in P. danubianum . Finally, a granular microsculpture in the radial interspaces occurs in P. magnei sp. nov., P. jansseni sp. nov., and P. danubianum . It is particularly well developed in P. jansseni sp. nov., being granulations larger and denser, often coalescent ( Fig. 13E 2 ). They form commarginal bands with variable density ( Figs. 13E 1 , 14 ).

Procardium magnei sp. nov. and P. jansseni sp. nov. are also similar in shape, equidimensional and weakly inequilateral. Also P. danubianum has a similar shape, but only in the younger stages, becoming somewhat elongate and inequilateral with growth, while P. kunstleri is marked inequilateral and oblique.

Stratigraphic and geographic range.— Procardium magnei sp. nov. is known from the Burdigalian of the Aquitaine Basin, but probably ranging from Aquitanian to Langhian, Miocene.

Figures

Fig. 15. Cardiid bivalve Procardium magnei sp. nov. from early Burdigalian (Miocene) of Saucats, “La Coquillière”, France. A. Holotype, PH 11708, external (A1), internal (A2), and umbonal (A3) views, details of sculpture (A4) and right hinge (A5). B. Paratype, PH 63240, external (B1), internal (B2), and posterior (B3) views. C. Paratype, RGM.794098, external view (C1), detail of sculpture (C2) and microsculpture (C3). Scale bars: A1–A3, B, C1, 50 mm; A5, C2, 20 mm; A4, 10 mm; C3, 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. 13. Cardiid bivalve Procardium jansseni sp. nov. from Langhian (Miocene) of Winterswijk, Miste (except F that is from Limburg, Beringe, borehole Beeringen DB15 [B58B008]), The Netherlands. A. Holotype, RGM.1309269 (van der Voort collection), umbonal fragment. B. Paratype, RGM.225756, anterior fragment. C. RGM.1309415 (van der Voort collection), umbonal fragment, hinge missing. D. RGM.1309416 (van der Voort collection), umbonal fragment. E. Paratype, RGM.225755, anterior fragment (E1) and detail of microsculpture (E2). F. RGM.794094 (Rijks Geologische Dienst collection), median fragment. G. RGM.1309417 (van der Voort collection), anterior fragment. H. RGM.794092.a, median fragment. I. Paratype, RGM.225754, posterior fragment. J. RGM.1309991 (ter Poorten collection), posterior fragment. K. RGM.1309418 (van der Voort collection), posterior fragment. Scale bars: A–D, E2, F–K 10 mm; E1, 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. 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.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.

Fig. 14. Cardiid bivalve Procardium jansseni sp. nov. Graphic reconstruction of a right valve based on 12 fragments from Langhian (Miocene), The Netherlands, Miste, and Beringe. Fragments covering the majority of valve surface. Scale bar 20 mm.