Bucardium grateloupianum, Perna, Rafael La, 2016

Perna, Rafael La, 2016, Bucardium grateloupianum n. sp. from the Lower Miocene of Aquitaine with taxonomic comments on some fossil species from Europe (Bivalvia, Cardiidae), Zootaxa 4178 (4), pp. 568-582 : 570-577

publication ID	https://doi.org/ 10.11646/zootaxa.4178.4.7
publication LSID	lsid:zoobank.org:pub:2B0A0406-30BA-4D09-9026-054272CAA221
DOI	https://doi.org/10.5281/zenodo.5673932
persistent identifier	https://treatment.plazi.org/id/1C20AE74-FF9C-5B41-F9E1-B925BB5E3495
treatment provided by	Plazi
scientific name	Bucardium grateloupianum
status	sp. nov.

Treatment

Bucardium grateloupianum n. sp.

( Figs 2 View FIGURE 2 A–L, 3A–F)

1912 Cardium (Ringicardium) grateloupi Mayer, 1866 , sensu Cossmann & Peyrot, 115, pl. 22, figs 3–6.

1950 Ringicardium aquense Magne : 122 (nomen nudum).

2005 Cardium grateloupi —Lesport & Cahuzac, pl. 6, figs 9, 19.

non

1839 Cardium grateloupi Michelotti, 1839 = Venus cypria Brocchi, 1814 = Nemocardium cyprium ( Brocchi, 1814) . 1862 Cardium hoernesianum Grateloup in Hörnes, 1862 = Cardium hoernesianum Hörnes, 1862 . 1866 Cardium grateloupi Mayer, 1866 = Cardium hoernesianum Hörnes, 1862 . 1910 Ringicardium hoernesianum Hörnes, 1862 , sensu Schaffer, 1910: 66, pl. 32, figs 1, 2. 1910 Ringicardium hoernesianum var. elongata Schaffer , 67, pl. 32, fig. 3.

1936 Cardium (Ringicardium) grateloupi var. oligocenica Noszky, 1936: 88 , 111, pl. 6, fig. 7. 2003 Cardium hoernesianum Hörnes, 1862 , sensu Schultz: 517, pl. 75, fig. 1.

Type material. Holotype, RV, Burdigalian of St-Paul-lès-Dax (MNHN Sciences de la Terre A13845, d'Orbigny coll. 10986); Paratype 1, RV, Burdigalian of Mérignac (MZB 60206); Paratype 2, LV, Mérignac (MZB 60207).

Description. Shell moderately large, robust and convex; poorly elongate, inequilateral, slightly gaping. Umbo median, moderately large, barely prosogyrate. Antero-dorsal margin long, straight to slightly convex, barely sloping. Posterior margin moderately convex, ventral margin strongly convex, posterior margin consisting of some, usually six, rather strong, well developed, sharply ending digitations, dorsalward increasing in strength, formed by prolongations of posterior ribs; postero-dorsal margin short. Radial sculpture moderately robust, covering all shell surface.

Sculpture on antero-dorsal area consisting of seven or eight fine ribs, symmetrically triangular in cross-section, with interspaces of similar width. Following sculpture much stronger, of about 13 wide, convex ribs separated by narrow and flat interspaces; rib cross-section slightly asymmetrical, with wider, convex anterior side and narrower, steeper posterior side, then becoming almost symmetrical and flatter medially, and again markedly aymmetrical up to the postero-ventral transition.

Six posterior ribs flattish, strongly asymmetrical in cross-section, each rib with a thin, continuous laminar ridge on its posterior side; ridges finely and irregularly wavy; interspaces very narrow, deep. Commarginal sculpture consisting of fairly distinct growth striae, crossing ribs and interspaces, slightly crescent-shaped on posterior ribs.

Internal margin crenulate and serrate, finely antero-dorsally, in accordance with external ribbing. Adductor muscle scars ovate, of similar size; pallial line entire, poorly distinct. Hinge moderately strong, rather straight, with well developed lunular flap. Right valve with a deeply bifid cardinal tooth, two anterior triangular, elongate lateral teeth, dorsal one much weaker; one strong, posterior lateral tooth. Left valve with a cardinal, deeply bifid tooth, two anterior triangular, lateral teeth, dorsal one stronger; two posterior triangular, elongate posterior teeth, dorsal one much stronger. Lunule lanceolate, moderately deep, smooth; escutcheon small, mostly occupied by ligament.

Holotype: L 61 mm, H 53 mm; paratype 1: L 65 mm, H 56 mm; paratype 2: L 43 mm, H 36 mm.

Type locality. Saint-Paul-lès-Dax, Landes, SW France. The holotype is from a lot in the d'Orbigny coll. ( MNHN) from Saint-Paul-lès-Dax, labelled as " Cardium burdigalinum Lamarck, Falunien B ". The outcrops in the area of Saint-Paul-lès-Dax (SE of Bordeaux) are shallow-water, coarse-grained deposits (" falun ") of Aquitanian to Burdigalian age ( Poignant 1966). The paratypes are from Mérignac, a well known Burdigalian locality in the area of Bordeaux ( Folliot 1989; Cahuzac & Janssen 2010).

Other material. Mérignac, 4 vs (La Perna coll.); Mérignac, 1 v (ter Poorten coll. 1310); Mérignac, 2 vs (NHMW 1850.XXV.99); Léognan, 1 v (NHMW 1851.XVII.1324); Salles, 2 vs (NHMW 1851.XXIX.56); Léognan, 2 vs (NHMW 1860.XXIX.58); Saucats, 2 vs (NHMW no registration number).

Etymology. The species is named after the French naturalist Jean-Pierre Sylvestre de Grateloup (1782–1861), who was the first to recognise and name this species in schedis.

Comparison. The only species which Bucardium grateloupianum n. sp. surely deserves to be compared to is B. ringens ( Fig. 1 View FIGURE 1 ). In B. grateloupianum n. sp., the antero-dorsal margin is long, almost straight and only slightly sloping whereas it is shorter and distinctly sloping in B. ringens . The antero-dorsal area with fine radial ribs ( Fig. 2 View FIGURE 2 J) is much better defined in the new species, and the posterior digitations are coarser and less numerous with the dorsal one pointing upwards and extending above the umbo, in the large valves at least ( Fig. 2 View FIGURE 2 A–C, G, H).

The radial sculpture follows the same pattern as in B. ringens , but in the new species the medial ribs are mainly symmetrically convex and only becoming asymmetrical and then ridged near the posterior margin. The crescentshaped growth striae on the posterior ribs are well distinct in B. ringens but ill-defined in the new species ( Fig. 2 View FIGURE 2 C). Bucardium grateloupianum n. sp. is slightly elongate antero-posteriorly, particular at larger size, instead of being almost equidimensional as B. ringens , and with a larger maximum size (slightly exceeding 60 mm in length).

Some differences can be also seen in the hinge, which is straighter in the new species, with the posterior lateral tooth in the right valve further away from the cardinal teeth than in B. ringens ( Fig. 2 View FIGURE 2 F, I). Crenulation on the lunular flap is generally coarser and better developed in the new species ( Fig. 2 View FIGURE 2 K), but this character seems rather variable.

In B. ringens , right and left digitations touch each other at least in part ( Fig. 1 View FIGURE 1 E) whereas the posterior gape in B. grateloupianum n. sp. seems wider, with digitations not touching each other. Variations mainly regard the length and number of posterior digitations: they are typically well developed, up to six, but specimens with few, short digitations (3–4) ( Fig. 3 View FIGURE 3 A–C) and even almost mutic specimens are known ( Fig. 3 View FIGURE 3 D).

Nomenclatorial history. Bucardium grateloupianum n. sp. was first illustrated by Cossmann & Peyrot (1912: 115, pl. 22, figs 3–6) as Cardium (Ringicardium) grateloupi Mayer, 1866 . They tried, though unsuccessfully, to clarify the species’ identity, already confused at that time (“ Cette espèce a donné lieu a plusieurs confusions ”). As observed by Magne (1950), Cardium grateloupi was proposed by Mayer (1866: 71) as a replacement name for “ Cardium hoernesianum Grateloup ” of Hörnes (1862: 183, pl. 27, figs. 1a-c), from the Eggenburgian (Upper Miocene) of Austria, thought to be preoccupied by C. hoernesi Deshayes, 1858 . This is very clear from Mayer’s comments: “… je ferai remarquer que le C. Hörnesianum Grat. (Hörn., Foss. Mollusk. Von Wien, vol. II, p. 183, pl. XXVII, fig. 1) […] doit encore changer de nom, puisque le C. Hörnesi Desh. à la priorité de près d’un an ”.

Hörnes (1862) and Schaffer (1919: 66) explained that Grateloup sent Cardium specimens to the Hofmineralienkabinett in Vienna (the modern Naturhistorisches Museum), one year before his death. This material, labelled as Cardium hoernesianum Grateloup sp. nov., from the Burdigalian yellowish falun at Léognan, south of Bordeaux, is deemed to be conspecific with C. grateloupianum n. sp. Grateloup also annotated that his new species had been confused with Cardium burdigalinum Lamarck, 1819 .

Actually, some material labelled as " Cardium hoernesianum Grateloup ", all from the area of Bordeaux, is present at NHMW ( Fig. 3 View FIGURE 3 A–F). One lot, consisting of two worn valves, almost lacking the posterior digitations ( Fig. 3 View FIGURE 3 E, F), is from Léognan and was acquired in 1860 (as can be inferred from the registration number), i.e. one year before Grateloup’s death in 1861 ( Lesport et al. 2012). It could represent Grateloup’s original material, and their worn condition could explain why Hörnes (1862) applied Grateloup’s manuscript name to a different species (further discussed below), remarking that “ Die Wiener Exemplare gleichen vollkommen denen aus der Umgebung von Bordeaux, nur sind sie wie alle hiesigen Vorkommnisse verhältnissmässig grösser und dicker in der Schale ” ("The specimens from Vienna are completely identical to those from the Bordeaux area, but […] the shells are comparatively larger and thicker"). The correct authorship of C. hoernesianum should be then Hörnes, 1862, not Grateloup in Hörnes, given that Hörnes did not describe Grateloup's species, but a different one.

For Cardium grateloupi, Cossmann & Peyrot (1912) reported the following synonymy: Cardium burdigalinum Basterot, 1825 (non Lamarck), C. hoernesianum Grateloup, 1838 (non C. hoernesi Deshayes ), C. grateloupi Mayer, 1866 , and C. grateloupi Benoist, 1873 . Basterot (1825: 82, pl. 6, fig. 12) actually reported Cardium burdigalinum from the area of Bordeaux and it really is Lamarck’s burdigalinum , as discussed below. The second synonymous entry, " Cardium hoernesianum Grateloup, 1838 " does not exist. According to the citation (" Cat. Gir. ") by Cossmann & Peyrot, it was published in the catalogue of fossils from Gironde (Grateloup "1838"; published in 1839: Lesport et al. 2012), where only C. burdigalinum was listed. The third entry evidently refers to the species from Austria renamed by Mayer (1866), while the last one is the record of C. grateloupi from the falun of La Bréde and Saucats by Benoist (1873: 45), who evidently misapplied Mayer's name.

Cardium grateloupianum n. sp. was dealt with by Magne (1950), as Ringicardium aquense Magne, 1944 . While the older citation refers to Magne’s unpublished graduation thesis at the University of Bordeaux (1944), the same author failed to provide a nomenclatorially valid description in his later work; R. aquense Magne, 1950 is considered a nomen nudum, therefore. However, Magne has the merit of having realized that the species illustrated by Cossmann & Peyrot (1912) as Cardium grateloupi had never been described and that C. hoernesianum was a replacement name for a distinct Miocene species from Austria.

Noszky (1936: 88, 111, pl. 6, fig. 7) described Cardium (Ringicardium) grateloupi var. oligocenica from the Egerian (Chattian, Upper Oligocene ) of Eger, Hungary . The new variety was compared with C. grateloupi of Cossmann & Peyrot (1912) but the original material, consisting of a badly preserved internal mould, is definitely different from Bucardium grateloupianum n. sp. Further comments on this taxon and other cardiids from the Egerian of Hungary are reported below.

Finally, Cardium grateloupi Mayer, 1866 , is a primary homonym of C. grateloupi Michelotti, 1839 , which is considered a junior synonym of Venus cypria Brocchi, 1814 , now Nemocardium cyprium , from the Pliocene of Italy ( Hylleberg 2004; La Perna & D’Abramo 2011).

Distribution. In addition to Saint-Paul-lès-Dax and Mérignac, from where the type material comes, the study material is from Lèognan, Saucats and Salles, all well known fossiliferous localities in the Aquitaine basin ( Folliot 1989). The outcrops in the areas of Lèognan and Saucats are of Burdigalian age, though some of the Saucats outcrops include Late Aquitanian beds, while the outcrops in the area of Salles are Serravallian ( Poignant et al. 1997; Cahuzac & Cluzaud 1999; Cahuzac & Jannsen 2010). According to Cossmann & Peyrot (1912) and Magne (1950), this species is only known from Aquitanian and Burdigalian deposits. Most probably, the "Serravallian" material (NHMW) was mislabelled or its locality inaccurately recorded, considering that in some Miocene localities in SW France, the Burdigalian deposits are directly overlain by Serravallian beds ( Poignant et al. 1997: fig. 5).

The species was recently described as Cardium grateloupi by Lesport & Cahuzac (2005) from a rich molluscan assemblage of Early Burdigalian age at Martillac, south of Bordeaux. It is a shallow water assemblage of sandy substrate, comparable to the modern Sables Fins Bien Calibrés community, as defined in the Mediterranean by Pérès & Picard (1964).

The living B. ringen s, a tropical species as indicated by its West African distribution, is probably the direct descent of B. grateloupianum n. sp., which evidently also had warm water preferences, as inferred from the palaeoclimatic and palaeogeographic characteristics of the Lower Miocene fauna of the Aquitaine basin (Lauriat- Rage et al. 1993; Lozouet 2014).