Merklinia variabilis (F. von Hagenow, 1842)
HAGENOW, F. VON. 1842. Monographie der Rügen'schen Kreideversteinerungen. III.
Mollusken. Neues Jahrbuch für Mineralogie, Geognosie, Geologie und
Petrefakten-Kunde, 1842 : 528-575, pl. 9. [p. 552]
1842 Pecten variabilis Hagenow, 1842
1842 Pecten leonhardi Hagenow, 1842
1842 Pecten trisulcus Hagenow, 1842
1859 Pecten tricostatus Mueller, 1859
1902 Pecten (Aequipecten) pexatus H. Woods, 1902
1977 Chlamys (Merklinia) triformis Sobetski, 1977
1842 Pecten leonhardi Hagenow, 1842
1842 Pecten trisulcus Hagenow, 1842
1859 Pecten tricostatus Mueller, 1859
1902 Pecten (Aequipecten) pexatus H. Woods, 1902
1977 Chlamys (Merklinia) triformis Sobetski, 1977
Merklinia variabilis (von Hagenow, 1842); A. V. Dhondt & J. W. M. Jagt, 1996, Late Creatceous
macrofauna from the Hautes Fagnes area, plate 1, figure 12.
|
«8) P. variabilis nob. Lang Ei-rund, stark gewölbt und sehr schief, wodurch sich diese Art sogleich von der vorigen unterscheidet, mit welcher sie jedoch hinsichtlich der dreitheiligin Rippen grosse Ähnlichkeit hat; diese sind eben so, aber mit etwas mehr röhrigeren Stacheln besetzt und mit feinen Zähnen gesäumt, welche beide jedoch bei einem grösseren Exemplare, 2 Linien vom Rande entfernt, plötzlich aufhören. Die Rippen setlen über diesem glatten Saum fort und gleichen sich die Haupt- und Neben-Rippen zu fast gleicher Stärke aus, und zwar so, dass jede derselben wieder dreitheilig wird und aus einer höher gelegenen, glatten abgerundeten Leiste mit zwei etwas tiefer zu beiden Seiten liegenden, halbrunden Stäben besteht, welche letzte mit zarten, gebogenen Queer-Rippen bedeckt sind. Lng eines jungen, wohlerhaltenen Exemplars: 6"', Breite 4"'.»
FRIEDRICH VON HAGENOW, 1842
|
«Description. Small- to medium-sized species. Both valves with 9-12, commonly 11, ribs; these are subdivided into 3 - 7 almost equal riblets; their intercostal intervals are very narrow; the principal and side-riblets bear well-developed spines (long and small respectively). Valves acline to slightly prosocline with relatively large unequal auricles. Anterior auricle of right valve has a deep byssal sinus and 3 - 5 radial riblets parallel to hinge margin; posterior auricle of right valve smaller, triangular and almost rightangled. Anterior auricle of left valve is large and also has radial riblets.
Remarks. Complete specimens easily recognised by their slightly prosocline disc shape, the number of ribs (13) and by the extreme subdivision of the ribs into fine costellae. Distinguished from other Merklinia species in having longer spines on the principal ribs and a height greater than its width. M. aspera (Lamarck) (Albian-Cenomanian) has many more ribs (PI. 20, figs 1-2; Text-fig. 7.4B). Occurrence. Turonian-Maastrichtian; southern England from Devon to Kent, also East Anglia.» 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. 124, 125]
|
Merklinia sp. cf. variabilis (von Hagenow); R. J. Cleevely & N. J. Morris, 2002, Introduction to molluscs and bivalves, plate 20, figures 13, 14.
|
«Merklinia variabilis, despite its name, is not very variable: the ribnumber varies from 9 to 12, but is almost always 11; the ribs are subdivided and on each side of the principal ribs there are 1 to 3 side-riblets.
It is likely that the small specimen from East Harnham (Wilts.) described by H. WOODS (1902, p. 191, pl. 36, fig. 8) as Pecten (Aequipecten) spec. is also a Merklinia variabilis for the following reasons :
Differentiation:
M. variabilis is differentiated from the other Merklinia species by the longer spines on the principal ribs and because U. P. D. ) › W, whereas the other species have a more orbicular shape. M. aspera (LAMARCK) has more ribs, and M. perornata (COTTREAU) has relatively smaller auricles. Palaeogeographical note : This species seems to be limited to the Northern European'slhite Chalk ("Schreibkreide"). It is found in Turonian to Lower Maastrichtian strata in Great Britain, Campanian to Upper Maastrichtian in Limburg (Belgium - The Netherlands) (not however, in Hainaut, Paris Basin), Senonian to Maastrichtian in North Germany, Turonian to Maastrichtian in Denmark, Senonian in Saxony and Czechoslovakia (very rare in these areas, but the numbef of specimens could be small because of the limited occurrence of marine Senonian deposits), Campanian to Maastrichtian in Poland and Maastrichtian of Süestern Ukraine (U. S. S. R.). Generic attribution: Pecten variabilis VON HAGENOW, 1842 is so similar in ornamentarion and general shape to Pecten asper LAMARCK, type-species of Merklinia SOBETZKI, that its correct name becomes Merklinia variabilis (VON HAGENOW, 1842).» DHONDT, A. V. 1976. Systematic revision of the Chlamydinae (Pectinidae, Bivalvia, Mollusca) of the European Cretaceous. Part 4: Merklinia. Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, 51 (7): 1-38, pls. 1-2. [p. 25, 26]
|
Merklinia variabilis (F. von Hagenow); A. V. Dhondt, 1976, Systematic revision of the Chlamydinae of the European Cretaceous, Part 4: Merklinia, plate 1, figure 2; plate 2, figures 1a, 1b.
|