Lyriochlamys mantelliana (Orbigny, 1847)
ORBIGNY, A, D'. 1844-1847. Paléontologie francaise. Description des Mollusques Rayonnés fossiles. Terrains crétacés. III. Lamellibranches. 807 p., pls. 237-489. Chez Arthus Bertrand, Libraire-Éditeur. Paris. [p. 619, pl. 440, figs. 8-11]
1833 Pecten concentricus Woodward, 1833
1847 Pecten mantellianus Orbigny, 1847
1847 Pecten mantellianus Orbigny, 1847
A. d'Orbigny, 1844-1847, plate 440.
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«Pecten, Mantell, 1822. Sussex, pl. XXV, f. 6; pl. XXVI, f. 7.
P. testa ovatâ, transversâ, maximè deprèssâ, radiatim 18— costatâ; costis subcomplanatis, angustatis, interstitiisque latis , complanatis, transversim costatis, punctatis; auriculis inaequalihus. Dimensions. Largeur, 35 millim. — Par rapport à la largeur: longueur, 89/100; épaisseur, 20/100; — Angle apicial, 90°. Coquille ovale, transverse, très-déprimée, mince, fragile, ornée de dix-huit côtes rayonnantes, à peine saillantes, étroites, entre lesquelles sont de larges espaces unis, striés en travers, et comme granulés par des points en relief. Au bord les côtes disparaissent et sont remplacées par de très-forts plis concentriques d'accroissement.
Rapports et différences. Cette espèce est voisine, par sa forme, du P. nitidus, mais elle s'en distingue par ses côtes plus égales, moius nombreuses et plus largement espacées. Localité. M. Dutomple a recueilli cette jolie espèce à Chavot (Marne), dans la craie blanche ou étage sénonien le plus supérieur. Explication des figures. Pl. 440 , fig. 8.6 Coquille de grandeur naturelle. De la collection de M. Dutemple. Fig. 9. La même, vue de profil. Fig. 10. Une portion grossie. Fig. 11. Profil de la même.» ALCIDE D'ORBIGNY, 1847
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«Description. Medium-sized, very flattened species covered with 11-30 narrow, flattened, radial ribs and with a few distinctive raised, concentric growth lines.
Remarks. Distinguished from other species by being much flatter, particularly the right valve, and in having well-developed elevations formed by the few growth lines. The concentric structures on the auriculae are typically more prominent than the radial elements. M. mantelliana can be separated from the closely related M. cretosa by the lack of scales on its ribs, while the lack of elevated growth lines distinguishes the flatter examples of M. cretosa. Occurrence. Santonian-Maastrichtian, O. lunata Zone; widespread in southern England and East Anglia; Dhondt (1973a, p. 98) stated that all the specimens she had studied had been found in a very fine white chalk.» CLEEVELY, R. J. & N. J. MORRIS. 2002. Introduction to molluscs and bivalves. In A. B. Smith & D. J. Batten (Eds.): Fossils of the Chalk, 99-160. The Paleontological Association. London. [p. 121]
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Mimachlamys mantelliana (d'Orbigny); R. J. Cleevely & N. J. Morris, 2002, Introduction to molluscs and bivalves, plate 20, figures 10, 11.
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«The concept of Lyriochlamys employed in the present study encompasses species placed by Dhondt (1973) in Chlamys (Mimachlamys) as well as Pecten semptemplicatus and Pecten ternatus Muenster in Goldfuss, 1833, placed by Dhondt (1972b) in "Lyropecten (Aequipecten?)." Mimachlamys Iredale, 1929 (type species, Pecten asperrimus Lamarck, 1819, Holocene, Indo- Pacific), is an extant genus that originated in the Eocene with characters not present in the Mesozoic taxa (Waller, 1991)»
WALLER, T. R. & L. MARINCOVICH JR. 1992. New species of Camptochlamys and Chlamys (Mollusca: Bivalvia: Pectinidae) from nearthe Cretaceous/Tertiary boundary at Ocean Point, North Slope, Alaska. Journal of Paleontology, 66 (2): 215-227, figs. 1-5. [p. 224]
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