Euthymipecten astierianus (Orbigny, 1850)
ORBIGNY, A. D'. 1850. Prodrome de Paléontologie stratigraphique universelle des animaux mollusques et rayonnés. Deuxième Volume. 427 pp. Victor Masson. Paris. [p. 83]
«*392. Astierianus, d'Orb., 1847. Grande espèce, presque aussi large que haute, à côtes inégales alternes. France, environs de Castellanne (B.-Alpes), St-Auban (Var).»
ALCIDE D'ORBIGNY, 1850
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«Description: Right valve suborbicular, covered with 16 to 21 primary radial ribs and several irregular secondary intercalary ribs; fine commarginal ornamentation forms spine-like structures at the intersection with primary and secondary radial ribs; anterior auricle elongate and with well developed byssal sinus, posterior auricle smaller and with almost right angle, both covered with strong commarginal lines which follow the exterior margins; less developed radial lines can also be seen.
Left valve somewhat more flattened than the right, mainly bearing only narrow radial ribs, also 16 to 21 in number, divided by broad interspaces; towards the margin rare intercalary ribs are present; anterior auricle with acute outer angle and covered with radial and commarginal lines, posterior auricle somewhat smaller. Discussion: Already in 1871 PICTET and CAMPICHE placed the species Pecten Euthymi PICTET, 1867 in the synonymy of P. Astierianus D'ORBIGNY, 1850. Both taxa show the same ornamentation (COTTREAU, 1934-35) and are based on incomplete specimens, yet they agree in all details. The only specimen figured in literature with more or less complete auricles is in COTTREAU (1934, text-fig. on p. 69). Complete auricles are preserved on specimens in the COQUAND colI. (MAFI), and they prove beyond doubt that the auricle reconstruction made by PICTET (1867, pI. 21, figs. 1a, 1b) is inaccurate.
The generic attribution of Pecten Astierianus has been discussed by GILLET (1924), who placed it in Prospondylus ZIMMERMANN, 1886. According to NEWELL in MOORE (1969) this genus is synonymous with Pseudomonotis VON BEYRICH, 1852 and is restricted to the Palaeozoic. MONGIN (1980) rediscussed the problem, but did not come to any new conclusions and accepted the generic interpretation previously proposed by GILLET. Euthymipecten astierianus is obviously a pectinid which was generally free living in adult stages. On none of the specimens is there any trace of attachment on the right valve near the umbo. Only occasional byssal attachment could have existed for E. astierianus in adult stages. This is why E. astierianus does not belong to the genus Eopecten. In conclusion it cannot be included in the genera suggested by earlier authors: GILLET, COTTREAU, DIMITROVA and MONGIN (see synonymy). E. astierianus show definite similarities with the congeneric Albian-Cenomanian "Pecten (Aequipecten) beaveri" SOWERBY, 1817 figured and described in WOODS (1902, p. 188, pI. 38): suborbicular valves and numerous straight ribs, primary, secondary and in E. beaveri even frequently tertiary. Both species seem to have lived in very fine grained sediments as we can ascertain from finding E. beaveri in the Gault clays or in the Lower Chalk, and E. astierianus in the "lithographic" limestone at Berrias, or in chalky marls in Eastern Sardinia. Distribution: Pecten Astierianus was originally described from beds dated as "Néocomien A" at Castellane (Alpes-de-Haute-Provence) and at Saint-Auban (Alpes-Maritimes). P. Euthymi was described by PICTET from Berrias (Ardèche), without statement about the precise level at which the specimens were collected. LE HÉGARAT in BUSNARDO et al., 1965, LE HÉGARAT, 1980 and in GALBRUN et al., 1986, indicated "Prospondylus euthymi" as occurring in the Callisto Subzone (i.e. uppermost Berriasian) in the type-section of the Berriasian.
Since the original descriptions (as P. Astierianus and P. Euthymi) the species has been recorded from the following regions (taking into consideration only undoubted occurrences): Berriasian of the Ardèche (France), of Justistal (Thuner See, Switzerland), Valanginian of the Alpes-Maritimes and Alpes-de-Haute-Provence (France), Sardinia, Bulgaria, Morocco. The stratigraphic range of E. astierianus seems therefore to be restricted to the (Late?) Berriasian - Valanginian interval. The original specimens of P. Astierianus came from localities which do not contradict a Berriasian - Valanginian age. The stratigraphic distribution indicated by GILLET (1924) (Tithonian-Gargasian) seems unconfirmed. Probably she had included longer ranging Eopecten species in her interpretation of "Prospondylus euthymi". BESAIRIE (1972), in fossil-lists, mentioned occurrences of "Prospondylus euthymi" from the uppermost Aptian (Clansayesian) of Madagascar. They seem doubtful and disagree with other definite occurrences.» DHONDT, A. V. & I. DIENI. 1988. Early Cretaceous bivalves of eastern Sardinia. Memorie di Scienze Geologiche, 40: 1-97, pls. 1-13, text-figs. 1-25. [p. 31, 32]
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Euthymipecten astierianus (d'Orbigny); A. V. Dhondt & I. Dieni, 1988, Early Cretaceous bivalves of eastern Sardinia, plate 6, figures 14a-14c, 15, 16a, 16b.
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