Praechlamys valoniensis (Defrance, 1825)
DEFRANCE, J. L. M. 1825. In M. de Caumont, Memoire geologique sur quelques terrains de la Normandie occidentale. Mémoires de la Société Linnéenne du Calvados, 2: 447-597. [p. 507, pl. 22, fig. 6]
1825 Pecten gervilii Defrance, 1825
1825 Pecten valoniensis Defrance, 1825
1838 Pecten lugdunensis Michelin in Leymiere, 1838
1858 Pecten cloacinus Quenstedt, 1858
1858 Pecten disparilis Quenstedt, 1858
1860 Pecten falgeri Stoppani, 1860
1860 Pecten janiriformis Stoppani, 1860
1860 Pecten aviculoides Stoppani, 1860
1860 Pecten barnenesis Stoppani, 1860
1860 Pecten winkleri Stoppani, 1860
1866 Pecten etheridgii Tawney, 1866
1866 Pecten suttonensis Tawney, 1866
1825 Pecten valoniensis Defrance, 1825
1838 Pecten lugdunensis Michelin in Leymiere, 1838
1858 Pecten cloacinus Quenstedt, 1858
1858 Pecten disparilis Quenstedt, 1858
1860 Pecten falgeri Stoppani, 1860
1860 Pecten janiriformis Stoppani, 1860
1860 Pecten aviculoides Stoppani, 1860
1860 Pecten barnenesis Stoppani, 1860
1860 Pecten winkleri Stoppani, 1860
1866 Pecten etheridgii Tawney, 1866
1866 Pecten suttonensis Tawney, 1866
J. L. M. Defrance, 1825, plate 22.
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«Les fossiles ne sont pas aussi variés dans le calcaire de Valognes que dans les dilférents systemes qui le surmontent: les coquilles y sont pour la plupart à I'état de moule intérieur, indéterminables, el leur test disparu est remplacé presque constamment par des cristaux de spath calcaire. Les mieux caractérisées sont: le Plagiostoma Valoniensis et le Pecten Valoniensis (Defr.), que j'ai figurées pl. 22, nº. 6 et 7.»
JACQUES LOUIS MARIN DEFRANCE, 1925
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Discussion: This species was originally referred to Chlamys RÖDING, but this, according to WALLER & MARINCOVICH (1992), is a Cenozoic genus. Taxonomy of Mesozoic Chlamidinae is not yet resolved (see discussion in MCROBERTS, 2011, p. 648), and thus the species here described is provisionally referred to Praechlamys since the shells lack strong antimarginal sculpture. Radial costae are fewer than in Hettangian and Sinemurian specimens from the same locality (DAMBORENEA, 2002, pl. 8, figs. 9-15; compare figs. 3.t and 3.u in RICCARDI et al., 2004), intervals are wider and commarginal lines more conspicuous. Also the anterior auricle is relatively shorter in the material here described. All these differences are well within the observed morphologic variation of similar pectinids (see JOHNSON, 1984). Open nomenclature is used on account of the few specimens available, which have narrower radial costae and more convex right valve than in P. valoniensis (as understood by JOHNSON, 1984).
This species has fine commarginal threads intersecting the narrow radial costae similar to the ornamentation in Agerchlamys DAMBORENEA, 1993, but it can be distinguished from species of that genus by the equallysized auricles, lack of antimarginal ornamentation and fewer radial costae. Agerchlamys inspecta (KIPARISOVA, in KIPARISOVA et al., 1966, pl. 17, figs. 7-11, pl. 18, figs. 1-2) from the Carnian-Norian of Siberia has a typical Agerchlamys ornamentation with more radial ribs. The lack of antimarginal ornamentation also distinguishes this species from similar ones referred to Lyriochlamys SOBETSKI (see discussion in MCROBERTS, 2011). This species ranges from Late Triassic to Pliensbachian in the river Atuel region (DAMBORENEA, 2002; RICCARDI et al., 2004). Praechlamys valoniensis has a similar stratigraphical range in Europe and elsewhere, spanning the Triassic-Jurassic boundary (see for instance IVIMEY-COOK et al., 1999, p. 105, pl. 14, figs. 8-10; YIN & MCROBERTS, 2006, p. 109-110, figs. 4.5-4.12). DAMBORENEA, S. E. & M. O. MANCEÑIDO. 2012. Late Triassic bivalves and brachiopods from southern Mendoza, Argentina. Revue de Paléobiologie, 11: 317-344, pls. 1, 2. [p. 325, 326]
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Praechlamys? cf. valoniensis (Defrance, 1825); S. E. Damborenea & M. O. Manceñido, 2012, Late Triassic bivalves and brachiopods from southern Mendoza, Argentina, pl. 1, figures 14a, 14b.
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«Description.— Medium-sized (maximum length = 36 mm. maximum height = 36 mm), approximately equilateral, height exceeding length in early ontogeny, gradually becoming equal to length in adult shells; inequivalved with left valve more inflated than right; umbonal angle about 908; right anterior auricle with large byssal notch, ornamented by four or five radial ribs, larger than obtusely pointed posterior auricle; both valves bearing large number of radial plicae that vary in strength and spacing, increasing in number by intercalation of secondary ribs, varying from 24 at 15 mm from beak to about 70 at 35 mm from beak.
Material examined.— Including the seven catalogued specimens, the collection consists of 10 specimens: four left valves, six right valves, all preserved as internal or external molds; CUGB2132, CUGB3033b, CUGB2051b, CUGB2052, CUGB2253, CUGB2154, CUGB2059. Occurrence.— Localities BH-3a and BH-4 of section A (transitional Rhaetian-Hettangian to lower Hettangian). Discussion.— Chlamys valoniensis has been reviewed at length by Johnson (1984) and more recently, as a species within Praechlamys Allasinaz, 1972, by Damborenea, 2002. Although the Tibetan forms exhibit somewhat more closely spaced and finer radial plicae than some specimens attributed to this species, the rib characters fall within the limits of this highly variable species. Chlamys valoniensis has a cosmopolitan distribution and is found in New Zealand and South America (e.g., Damborenea and Manceñido, 1992; Aberhan, 1994; Riccardi et al., 2004), alpine and northwest Europe (e.g., Johnson, 1984; Hodges, 2000), and western Canada (e.g., Aberhan, 1998), ranging from Rhaetian to Hettangian.» YIN, J. & C. A. MCROBERTS. 2006. Latest Triassic-Earliest Jurassic bivalves of the Germig formation from Lanongla (Tibet, China). Journal of Paleontology, 80 (1): 104-120. [p. 109, 110]
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Chlamys valoniensis (Defrance, 1825); J. Yin & C. A. McRoberts, 2006, Latest Triassic-Earliest Jurassic bivalves of the Germig formation from Lanongla, figures 4.5-4.12.
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«When having made a huge and painstaking work on revision of Jurassic representatives of Chlamydidae of Europe, A. Johnson (1984) proposes combining all known species into three species: Chlamys (Chlamys) textoria (Schlotheim, 1820); Chl. (Chl.) valoniensis (Defrance, 1825) and Chl. (Chl.) pollux (Orbigny, 1850), including the rest in their synonymy. Thus, this author includes in the synonymy of Chlamys (Chlamys) textoria (Schlotheim, 1820) more than eighty names of specific groups, including species the validity of which is recognized by us. Following the principle suggested by A. Johnson (1984), also Triassic representatives of Chlamys, distinguished by Allasinaz (1972) within subgenus Praechlamys, ought to be included as well within the synonymy of Chlamys (Chlamys) textoria (Schlotheim, 1820).»
KASUMZADEH, A. A.. 2003. Advance in research of mesozoic bivalve mollusks in Azerbaijan (Order Pectinoida: Revision and Systematics). 111 pp. Baku [Translated by Rosanne D’Aprile Johnson, VIARC, Smithsonian Institution]. [p. 47]
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«2. DIAGNOSIS
Distinguished from both Ch. (Ch.) pollux and Ch. (Ch.) textoria by the lack of ornament on the plicae.
3. DESCRIPTION
Disc sub-ovate, higher than long, early in ontogeny, becoming sub-orbicular (text fig. 158) near maximum height of 77 mm (ENSM). Umbonal angle variable (text fig. 159), increasing during ontogeny to produce slightly coneave dorsal margins. Disc flanks moderately high and ornamented with vertical striae.
Slightly inequilateral, posterior sector somewhat larger; inequivalve, left valve moderately convex, right valve almost flat. Intersinal distance greater in left valve than right, increasing at a decreasing rate in both (text figs. 160, 161). Depth of byssal notch variable, moderate to large (text fig. 162). Auricles well demarcated from disc, approximately equal in size. Anterior auricles meeting hinge line at an acute angle; posterior auricles meeting hinge line at an obtuse angle. Anterior auricle of right valve meeting disc at an acute or right angle; remaining auricles meeting disc at an acute angle. Anterior auricles bearing 4-6 radial costae. Height of anterior auricle and lengh of anterior hinge increasing at a markedly decreasing rate (text figs. 163, 164). Length of posterior hinge increasing with similar but less marked allometry (text fig. 165). Both valves bearing a variable number of radial plicae (PI. 9, figs. 1-6), increasing in number by intercalation from between 20 and 30 early in ontogeny. Right valve with 31-36 at L: 20, about 39 at L: 40, about 49 at L:60, up to a maximum of 52 at L: 67.5 (ENSM). Left valve with 36-45 at L: 20, 44-65 at L: 40, 52-72 at L: 60, up to a maximum of 79 at L: 68 (ENSM). Shell thickness moderate. 4. DISCUSSION
The original figure of 'Pecten' Valoniensis DEFRANCE is a poor reproduction of an internal view of a left valve. Metric proportions (1) plot within the ränge of the species described in Section 3 and LEYMERIE (1838) and DUMORTIER (1864), both French authors who may have had access to the type material, have applied the name to figured specimens which undoubtedly belong to the latter species. Bearing this in mind and the fact that the horizon of derivation (Calcaire de Valognes) is one from which numerous examples of the species described in Section 3 have been recovered (see Section 7), DEFRANCE's name can be confidently applied as senior synonym to the latter species, despite the lack of diagnostic features in the original figure. Mr. P. HODGES will shortly be designating a neotype (see above).
The original figure of 'P.' lugdunensis MICHELIN is very reminiscent of Pseudopecten (Ps.) equivalvis (q. v.). However, DUMORTIER (1864), who appears to have examined the type material, has stated that MICHELIN's species is in fact equivalent to Ch. (Ch.) valoniensis and this view has been taken by later authors (e. g. STAESCHE, 1926) who may also have examined the type material. The anomalously low number of plicae in the right valve (25 at L: 45.5) and the high I R/L (2) of the original figure in comparison to Ch. (Ch.) valoniensis might be the result of respectively, preservation as an internal mould and inaccurate Illustration. In view of the somewhat equivocal position of MICHELIN's species, TERQUEM and PIETTES's (1865) unillustrated record of 'P.' lugdunensis can only tentatively be placed in synonymy. The original figure of 'P.' acutauritus SCHAFHÄULT seems to depict an abraded specimen of Ch. (Ch.) valoniensis and what is apparently one of SCHAFHÄULT's syntypes (BSPHG; AS IX 42; PI. 9, Fig. 3) undoubtedly belongs to the latter species. Metric proportions of the original figure (3) are inseparable from Ch. (Ch.) valoniensis. The original figure of 'P. ' dispar TERQUEM depicts a right valve with 41 plicae at L: 42 which has resemblances to both Ch. (Ch.) valoniensis and Ch. (Ch.) textoria. The specimen referred to TERQUEM's species by BISTRAM (1903) undoubtedly belongs in Ch. (Ch.) valoniensis and all but one (pl. 14, fig. 10, which has imbricate lamellae and is thus closer to Ch. (Ch.) textoria) of LENTINI's (1973) examples of Ch. (Ch.) dispar are similarly referable. However, in view of the fact that TERQUEM's original figure has an abnormally high IL/L and AH/L (4) some doubt must remain as to his hypodigm until the type material is located. With the possibility of confusion unillustrated records of TERQUEM's species in TERQUEM and PIETTE (1865), COSSMANN (1904), Joly (1907) and DECHASEAUX (1936) can only tentatively be placed in synonymy. It has proved impossible to trace the original reference to 'P.' Falgeri MERIAN. Specimens figured under this name by STOPPANI (1860) and CAPELLINI (1866) are clearly representative of Ch. (Ch.) valoniensis but BISTRAM's (1903) figure bears some resemblance to Pseudopecten (Ps.) equivalvis. It is not clear which, if any, of these authors has examined the type material so the position of MERIAN's species is uncertain. Consequently unfigured records of his species in LANQUINE (1929) and VECCHIA (1945) can only be provisionally synonymised. The position of 'P.' janiriformis STOPPANI is also in doubt. Although the original figure is available and resembles Ch. (Ch.) valoniensis, CAPELLINI (1866), who worked in the same field area (N. Italy) as STOPPANI and who may have examined the latter's type material, has applied his specific name to specimens which are closer to Ch. (Ch.) textoria. Whether or not they correspond to the original hypodigm for 'P.' janinformis, specimens referred to this species by LANQUINE (1929) undoubtedly fall within the present author's concept of Ch. (Ch.) valoniensis. CAPELLINI has also applied 'P.' aviculoides STOPPANI, a species founded on a fragment resembling Ch. (Ch.) valoniensis, to a specimen which has closer affinities with Ch. (Ch.) textoria. With this uncertainty over the position of STOPPANI's species 'P.' barnensis and 'P.' Winkleri, both of which show similarities to Ch. (Ch.) valoniensis, are best treated as only provisional synonyms. The sole observed syntype of 'P. ' cloacinus QUENSTEDT (GPIT 2-1-33; Pl. 9, Fig. 5) is indistinguishable from Ch. (Ch.) valoniensis by the number of plicae on the left valve (44 at L: 36) and by metric proportions (5). The number of plicae in 'P.' Suttonensis TAWNEY (sole observed type, IGS 7830; PI. 9, Fig. 4) and 'P.' Uhligi GEMMELLARO and DI BLASI has not been measured but appears to be within the range of Ch. (Ch.) valoniensis of comparable size. Metric proportions (6 and 7 respectively) are indistinguishable from the latter species. 'P.' sp.; TROEDSON was compared with Ch. (Ch.) valoniensis and in view of the horizon of derivation (Rhaetic) it seems very likely to be a representative of this species. The affinities of 'P.' disparilis QUENSTEDT and 'P. ' Etheridgii TAWNEY are discussed under Camptonectes (C.) subulatus. 5. STRATIGRAPHIC RANGE
Ch. (Ch.) valoniensis is first recorded from the L. Rhaetic Westbury Formation of Glamorgan and Gloucestershire, where it is common. In the U. Rhaetic Lilstock Formation of the same area it is rare but records from the 'Rhaetic' of Lombardy (STOPPANI, 1860), Spezia (BM L14938), Provence (LANQUINE, 1929), the Pyrenees (DUBAR, 1925), Belgium (JOLY, 1907) and Swabia (GPIG, GPIT) may include specimens from equivalent horizons as also may records from the 'Rhaeto-Lias' of Spezia (CAPELLINI, 1866) and Lombardy (VECCHIA, 1945). The species occurs almost throughout the type section of the Rhaetian in the Kendelbach Gorge, Austria (MORBEY, 1975).
In the Jurassic Ch. (Ch.) valoniensis is known from the Planorbis zone (Hettangian) in the Rhone Basin (DUMORTIER, 1864; ROMAN, 1926), N. Italy (BISTRAM, 1903) and S. Wales (WOBBER, 1968). 'Hettangian' records from S. France (LEYMERIE, 1838; JAUBERT, 1868; ROMAN, 1950), E. France (DECHASEAUX, 1936) and N. W. France (DEFRANCE, 1825b) probably also stem from this zone. The species is known from the Angulata zone of Bavaria (WINKLER, 1886) but specimens recorded by TERQUEM and PIETTE (1865) from this horizon and from the Sinemurian in E. France are only possibly conspecific (see Section 4). There is however no reason to doubt the conspecific Status of at least some of the specimens recorded by DECHASEAUX (1936) from the Sinemurian of Lorraine. Since the latter is the latest stage-defined record of Ch. (Ch.) valoniensis it is doubtful whether 'L. Lias' records in GEMMELARO (1878) and TRAUTH (1909) include any specimens from the L. Pliensbachian.» JHONSON, A. L. A. 1984. The palaeobiology of the bivalve families Pectinidae and Propeamussiidae in the Jurassic of Europe. Zitteliana, 11: 1-235, pls. 1-11. [p. 180-184]
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Chlamys (Ch.) valoniensis (Defrance, 1825); A. L. A. Jhonson, 1984, The palaeobiology of the bivalve families Pectinidae and Propeamussiidae in the Jurassic of Europe, plate 9, figures 1-6.
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«Coquille arrondie, équilatérale, très-inêquivalve, un peu plus large que longue, ordinairement, quand elle est adulte; angle apicial un peu plus grand que 90º.— La valve droite ou supérieure est assez bombée; elle est ornée de 22 à 24 côtes principales, entre lesquelles se montrent çà et là d'autres côtes plus fines et qui remontent pourtant jusque bien près du crochet: le tout est recouvert de fines stries concentriques, très-apparentes surtout dans dans le fond des plis; quelquefois il n'y a pas de plis secondaires et les principales côtes se groupent par deux: en somme, une assez grande irrégularité se remarque dans la disposition de ces ornements, mais les fines stries transversales se voient toujours quand le test est conservé.— J'ai des échantillons de la longueur de 10 millim. où ce caractère est déjà très-nettement marqué; il est à noter que les côtes rayonnantes ne finissent point, en diminuant de valeur ou de volume, à mesure qu'elles se rapprochent du côté antérieur, comme dans beaucoup de pecten ou les dernières côtes ne sont plus que des plis insignifiants.— Chez le P. valoniensis, la dernière côte, du côté antérieur, est toujours la plus grosse et la plus saillante de toutes (voir les figures 1 et 2 , pl. IX); en dehors de cette côte la coquille présente une area couverte de petites stries transverses fort élégantes, area qui se reproduit du côté postérieur, au dessous de l'oreille, mais avec un moindre développement. Oreilles assez grandes, horizontales, semblables, ornées de plusieurs côtes transverses; le crochet dépasse de très-peu la ligne cardinale.
La valve gauche, ou inférieure, est tout à fait plane et porte les mêmes ornements que l'autre, seulement l'insertion d'une petite côte entre deux grosses y est beaucoup plus rare et la disposition par deux plus ordinaire. L'oreille antérieure ressemble à celle de la valve droite.— Celle postérieure est fortement échancrée pour le passage du byssus et laisse voir trois ou quatre lignes rayonnantes. Les oreilles de cette valve sont abaissées fortement sur un plan autre que celui de la valve même et brusquement séparées, par un ressaut, de la surface de la coquille, tout en restant sur un plan parallèle à celle-ci. Les bords de la coquille onduleux. Le relief des côtes paraît en creux sur la surface intérieure des valves, comme on peut voir à la fig. 4, pl. IX, qui représente une valve plane du P. valoniensis, vue du côté intérieur. Le P. valoniensis, tout en ayant une valve bombée et une valve plane comme les Janira, ne pourrait cependant pas être rangé dans cette subdivision, car la disposition des valves est ici complètement inverse: chez le P. valoniensis, c'est la valve inférieure gauche et portant l'échancrure du byssus, qui est plane: chez les Janira, c'est au contraire cette valve inférieure et échancrée qui est bombée, et réciproquement. Le P. valoniensis a été nommé el figuré (d'une manière insuffisante, il est vrai), dans un mémoire de M. de Gaumont, qui parut en 1825, dans les mémoires de la Société linnéenne du Calvados.— Il a été depuis bien souvent mentionné. M. Leyinerie, dans son mémoire sur la partie inférieure du système secondaire du département du Rhône, inséré dans les mémoires de la Société géologique de France, 1re série, tome 3, figure ce même pecten du Mont-d'Or lyonnais (pl. 24 , fig. 5.), et lui donne le nom de Pecten lugdunensis, en disant qu'il se rapproche beaucoup du P. valoniensis. Nous sommes forcés d'abandonner ce nom de P. lugdunensis, puisqu'il est liors de doute qu'il s'agit delà même espèce.— La coquille de Valognes , comme on le verra par la fig. 1 de ma planche IX, qui représente un grand exemplaire de cette localité, est un peu plus grande, et les côtes intermédiaires prennent dès lors un grand développement, mais c'est la seule différence que l'on puisse signaler. Les stries transversales trèsfines, que M. Leymerie remarque dans le P. valoniensis, existent tout aussi bien marquées dans le nôtre; la forme générale, celle des oreilles, les ornements accessoires, tout est identique.» DUMORTIER, E. 1864. Études Paléontologiques sur les Dépots Jurassiques du Bassin du Rhone. Première Partie. Infra-Lias. 1-187 p., pls. 1-30. F. Savy, Éditeur. Paris. [p. 59, 60]
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Pecten valoniensis (Defrance); E. Dumortier, 1864, Études Paléontologiques sur les Dépots Jurassiques du Bassin du Rhone, Première Partie, Infra-Lias, plate 9 figures 1-6 (above); plate 10, figures 1-3 (below).
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