Camptochlamys obscura (J. Sowerby, 1818)
SOWERBY,
J. & J. DE C. SOWERBY. 1812-1846. The Mineral Conchology of Great Britain;
or coloured figures and descriptions of those remains of testaceous animals or
shells. 7 vols., pls.
1-648 (and 2 bis). London. [vol. 3, p. 3, pl. 205, fig. 1]
1818 Pecten obscura J. Sowerby, 1818
1819 Pecten lamellosus J. Sowerby, 1819
1826 Pecten annulatus J. de C. Sowerby, 1826
1836 Pecten sublaevis Roemer, 1836
1837 Pecten concinnus Koch & Dunker, 1837
1850 Pecten germaniae Orbigny, 1850
1850 Pecten obrinus Orbigny, 1850
1852 Pecten circinalis Buvignier, 1852
1859 Pecten flamandi Contejean, 1859
1869 Pecten exaratus Terquem & Jourdy, 1869
1888 Pecten subannulatus Schlippe, 1888
1894 Pecten chavattensis De Loriol, 1894
1926 Camptonectes sowerbyi Staesche, 1926
1935 Camptonectes browni Cox, 1935
1936 Camptonectes richei Dechaseaux, 1936
1936 Camptonectes praecinctus Spath, 1936
1952 Camptonectes indicus Cox, 1952
1974 Camptonectes waggrankinensis Skwarko, 1974
1819 Pecten lamellosus J. Sowerby, 1819
1826 Pecten annulatus J. de C. Sowerby, 1826
1836 Pecten sublaevis Roemer, 1836
1837 Pecten concinnus Koch & Dunker, 1837
1850 Pecten germaniae Orbigny, 1850
1850 Pecten obrinus Orbigny, 1850
1852 Pecten circinalis Buvignier, 1852
1859 Pecten flamandi Contejean, 1859
1869 Pecten exaratus Terquem & Jourdy, 1869
1888 Pecten subannulatus Schlippe, 1888
1894 Pecten chavattensis De Loriol, 1894
1926 Camptonectes sowerbyi Staesche, 1926
1935 Camptonectes browni Cox, 1935
1936 Camptonectes richei Dechaseaux, 1936
1936 Camptonectes praecinctus Spath, 1936
1952 Camptonectes indicus Cox, 1952
1974 Camptonectes waggrankinensis Skwarko, 1974
J. Sowerby & J. de C. Sowerby, 1812-1846, plate 205.
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«SPEC. CHAR. Sub-orbicular, depressed, with obscure arched longitudinal rugae upon the surface; ears large.
SOMEWHAT longer than wide: the surface is dull, almost smooth; but it has some indications of diverging furrows. The edge is thick. Occurs upon the sandy Limestone slate of Stonesfield, near Oxford. My specimen was forwarded to me long since by Dr. Williams.» JAMES SOWERBY, 1818
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«2. AMENDED DIAGNOSIS
Distinguished from C. (Camptochlamys) clathratus by the fact that the radial striae extend no more than a few centimetres from the umbo and are thereafter replaced by divaricate striae.
3. AMENDED DESCRIPTION
Essentially similar to C. (Camptonectes) auritus. Differing by the presence of comarginal lamellae and radial striae (PI. 4, Fig. 22) of variable length, greater maximum height (122 mm, OUM J37483; ?206 mm, see Section 7), higher mean H/UA (text fig. 122), greater convexity of the left valve, isometric increase in anterior hinge length and right valve intersinal distance to give higher values of AH/L (text fig. 127) and IR/L (text fig. 124) late in ontogeny, isometric increase of anterior auricle height to give lower values of HAA/L (text fig. 126) late in ontogeny and allometric increase of posterior hinge length to give higher values of PH/L (text fig. 128) late in ontogeny. The remaining metric characters are plotted in text figs. 121, 123, 125.
Unlike C. (C.) auritus there appear to be no phyletic changes in metric proportions beyond an increase in size and a possible accentuation of allometric decrease in H/L in Tithonian as compared to Bathonian individuals. 4. DISCUSSION
A disjunct stratigraphic distribution with two distinct peaks in abundance (see Sections 5, 7) has resulted in the evolution of two taxonomic schemes (centred on species erected by the SOWERBYs for Bathonian and Tithonian examples) for M. and U. Jurassic representatives of the species described in Section 3. There is, however, no biological basis for maintaining a distinction and in the absence of any evidence for the existence of separate lineages such differences as exist between earlier and later populations (see Section 3) can be most parsimoniously explained in terms of phyletic evolution (see Section 10). Large L. Cretaceous forms (usually referred to Camptonectes cinctus J. SOWERBY) are probably also phyletic descendants but their systematics are excluded from this discussion because the present author has yet to survey the literature and has examined relatively few specimens. Suffice it to say that metric proportions (c) would plot within the ränge of Jurassic ontogenies if these were projected to larger sizes.»
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. 135, 136]
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Camptonectes (Camptochlamys) obscurus O. SOWERBY 1818); A. L. A. Johnson, 1984, The palaeobiology of the bivalve families Pectinidae and Propeamussiidae in the Jurassic of Europe, plate 4, figures 17-22, 24, 25.
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