Radulopecten varians (Roemer, 1836)
ROEMER, F. A. 1836. Die Versteinerungen des Norddeutschen Oolithen-Gebirges. 218 pp., pls. 1-16. Hannover [p. 68, pl. 3, fig. 19]
1836 Pecten varians Roemer, 1836
1852 Pecten beaumontinus Buvignier, 1852
1859 Hinnites clypeatus Contejean, 1859
1862 Pecten banneanus Étallon in Thurmann & Étallon, 1862
1862 Pecten pagnardi Étallon in Thurmann & Étallon, 1862
1862 Pecten qualicosta Étallon in Thurmann & Étallon, 1862
1863 Pecten perstrictus Étallon, 1863
1871 Pecten donezianus Borissak & Ivanoff, 1917
1936 Aequipecten buvignieri Dechaseaux, 1936
1852 Pecten beaumontinus Buvignier, 1852
1859 Hinnites clypeatus Contejean, 1859
1862 Pecten banneanus Étallon in Thurmann & Étallon, 1862
1862 Pecten pagnardi Étallon in Thurmann & Étallon, 1862
1862 Pecten qualicosta Étallon in Thurmann & Étallon, 1862
1863 Pecten perstrictus Étallon, 1863
1871 Pecten donezianus Borissak & Ivanoff, 1917
1936 Aequipecten buvignieri Dechaseaux, 1936
F. A. Roemer, 1836, plate 3.
|
«P. testa ovato-orbiculari convexo-plana radiatim striata, valva sinistra convexiore, striis subinaequalibus lineis concentricis in striarum longitudinalium dorso lamelloso-squamosis decussatis, auriculis inaequalibus longitudinaliter striatis.
Das Gehäuse ist eirund, oder fast ganz kreisrund; die Schalen sind heide gewölbt, die linke am meisten; beide sind mit zahlreichen ungleichen Längsstreifen besetzt, auf denen die concentrischen Linien blättrige Schuppen bilden; diese sind gewöhnlich nur am unteren Theile der Schalen deutlich, fehlen aber selten ganz. Die Ohren sind ungleich, längsgestreift und wenig queer-liniirt.
Ist gewöhnlich etwas kleiner, als das abgebildete Exemplar und findet sich im oberen Coral rag bei Hoheneggelsen, so wie am Galgenberge bei Hildesheim.» FRIEDERICH ADOLPH ROEMER, 1836
|
«2. AMENDED DIAGNOSIS
Differing from R. vagans, R. strictus and R. inequicostatus by the larger number of initial plicae and from all other species of Radulopecten by the existence of a non-plicate phase early in ontogeny.
3. AMENDED DESCRIPTION
Disc sub-ovate, higher than long, early in ontogeny growing allometrically (text fig. 177) to become sub-orbicular near the mnimum height of 33 mm (NM). Umbonal angle variable (text fig. 179), increasing slightly during ontogeny to produce concave dorsal margins. Disc flanks low.
Equilateral; inequivalve, left valve more convex than right, both low convexity. Intersinal distance greater in left valve than right; moderate sized byssal notch. Auricles well separated from disc, moderate in size, anterior slightly larger than posterior. Anterior auricles meeting hinge line and disc at a right angle; posterior auricles meeting hinge line at a right or obtuse angle and disc at an acute angle. Anterior auricles ornamented with 2–4 radial costae. Anterior hinge length moderate (text fig. 178). Right valve ornamented near the umbo with closely spaced comarginal striae and usually a large number of very fine radial striae. Latter developing into plicae at shell heights above about 10 mm to match those on the left valve (PI. 10, Fig. 1). Comarginal ornament tending to become reduced in the sulci. Leit valve also ornamented with comarginal striae near the umbo. All specimens possessing about 40 radial striae of which initially about 15 develop into narrow plicae to be followed, at a variable rate, by the remainder such that at H: 20 there are between 16 (OUM J1891) and 39 (OUM J9005) plicae and at H: 30 between 20 (BM 33423) and 40 (MNO 4293) plicae (PI. 10, Figs. 2,3). Comarginal striae expanding into lamellae on the crests of the plicae and tending to disappear in the sulci. Shell thickness moderate. 4. DISCUSSION
ROEMER's (1836) figure of 'Pecten' varians depicts a right vaIve whose number of plicae (ca. 28 at H: 22) and metric proportions (1) fall within the range of the species described in Section 3. Since ROEMER's name is the earliest available the latter is known hereinalter as Radulopecten varians.
There is some doubt over the afiinities of 'P.' Beaumontinus BUVIGNIER. This species and subsequent references thereto is discussed under R. strictus (MÜNSTER). Since ÉTALLON's (1862) 'P.' Banneanus was allied to BUVIGNIER's species and his 'P.' Pagnardi to MÜNSTER's species some doubt must remain as to the affinities of these species in spite of the fact that the figures of both appear to depict examples of R. varians. The figure of 'P.' qualicosta ÉTALLON undoubtedly depicts a specimen of R. varians as does de LORIOL's (1893) figure of a specimen (repository: Ecole Cantonale de Porrentruy, Switzerland) chosen as lectotype. CHAVAN's (1952) record of 'Chlamys' (R.) qualicosta appears to be a misnomer for R. fibrosus (q. v.). ÉTALLON's (1863) original reference to 'P.' perstrictus has proved impossible to trace. However, the description has been reiterated by DECHASEAUX (1936) together with a photograph of a type, which is indistinguishable from R. varians. The original reference to 'P. ' Urius SAUVAGE and RIGAUX has similarly proved impossible to trace but the species was redescribed and figured by the same authors (1872) and the number of plicae (30 at H: 21.5) and metric proportions (2) are within the range of R. varians. The holotype (M) of 'Aequipecten' Buvignieri DECHASEAUX (NM) has 22 plicae at H: 33 and metric proportions (3) which are indistinguishable from those of R. varians. The syntype series of 'P.' donezianus BORISSIAK and IVANOFF has not been studied but the photographs leave no doubt that the species should be synonymised with R. varians. The figure of 'Hinnites' clypeatus CONTEJEAN is of a right valve unlike that of any 'Hinnites' (= Eopecten) species but with a plical count (27 at H: 20) and metric proportions (4) which suggest that it may be a representative of R. varians. The affinities of 'P.' Thurmanni CONTEJEAN are discussed under R. vagans.» JOHNSON, 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. 196-198]
|
Radulopecten varians (Roemer 1836); A. L. A. Johnson, 1984, The palaeobiology of the bivalve families Pectinidae and Propeamussiidae in the Jurassic of Europe, plate 10, figures 1-3.
|