Neithea sexcostata (Woodward, 1833)
WOODWARD, S. 1833. An outline of the geology of Norfolk. 55 p., pls. 1-6. Printed and sold by John Stacy. Norwich [p. 48, pl. 5, fig. 29]
1833 Pecten striatocostatus Goldfuss, 1833
1833 Pecten sexcostatus Woodward, 1833
1847 Janira dutemplei Orbigny, 1847
1850 Janira carantonensis Orbigny, 1850
1850 Janira albensis Orbigny, 1850
1833 Pecten sexcostatus Woodward, 1833
1847 Janira dutemplei Orbigny, 1847
1850 Janira carantonensis Orbigny, 1850
1850 Janira albensis Orbigny, 1850
«Description. Much smaller than N. quinquecostata with a very convex right valve and flattened left valve. Six very salient principal ribs on both valves with deep intercostal intervals occupied by irregular, often poorly delineated ribs; all of the ribs are striated horizontally by riblets. The inwardly bent areas and the small equal auricles are similarly ornamented.
Remarks. Distinguished by its smaller size and the combination of salient primary ribs with more than four irregular, poorly delimited intercalaries.
Occurrence. Cenomanian-Campanian; southern England including Norfolk, Wiltshire, Dorset and Devon; frequent in the fine White Chalk, commonly occurring when other pectinids are rare.»
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. 128]
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Neithea (Neithea) sexcostata (S. Woodward); R. J. Cleevely & N. J. Morris, 2002, Introduction to molluscs and bivalves, plate 21, figures 7-9.
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«Material: Two right valves from Pinei, Lago di S. Croce [B67 (H = 19.4 mm; L = 21.2 mm) and B69 (H = 20.4 mm)].
Discussion: The N (N.) sexcostata specimens from Pinei have not very salient principal ribs, and about five intercalary ribs in each interval between these primary ribs. They agree with "form α" in Woods (1903).
Distribution: Recorded from Cenomanian to uppermost Mastrichtian, mainly in chalks but also in biocalcarenites. in Europe and extending into Kazakhstan and North Africa (Text-fig. 6).»
DHONDT, A. V. & I. DIENI. 1993. Non-rudistid bivalves from Late Cretaceous rudist limestones of NE Italy (Col di Schiosi and Lago di S. Croce areas). Memorie di Scienze Geologiche, 43: 165-241, pls. 1-20, text-figs. 1-18. [p. 197]
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Neithea (Neithea) sexcostata (Woodward, 1833); A. Dhondt & I. Dieni, 1993, Non-rudistid bivalves from Late Cretaceous rudist limestones of NE Italy (Col di Schiosi and Lago di S. Croce areas), plate 5, figures 5, 6.
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«Diagnosis.— Small Neithea-species with very convex right valve and flattened left valve. Both valves bear 6 very salient principal ribs with deep intercostal intervals, which are, in the same way as the inwardly bent areas and the equal auricles, covered with thin, very numerous, not very salient riblets which are crossed by slightly salient concentric growthlines'
To WOODS', 1903, pages 2I5 and 216, description nothing essential can be added. The differences which he noted between his forma o and forma α are probably little more than local variations: in Maastricht most specimens have the forma α, which WOODS thought to be limited to the Cenomanian. Discussion:
Variability.— The variability existing in this species is illustrated by WOODS' recognition of 2 formae. He saw those forms as stratigraphical varieties corresponding to different horizons and representing an evolutionary sequence; as mentioned above it is more probably a question of local varieties due to environmental factors.
Synonymy.— Pecten sexcostatus WOODWARD, although established without description is completely defined by its figures and localization. The booklet by WOODWARD was apparently not wellknown on the European continent because continental authors did not use WOODWARD's name before it was propagated by H. WOODS.
Pecten striatocostatus GOLDFUSS, plate 93, figures 2 c-e (non fig. 2, a, b, f, g) also belongs here: the confusion with N. striatocostata (GOLDFUSS) (see below under that species) resulted in many authors describing N. sexcostata sub N. striatocostata. GOLDFUSS' figures are not quite satisfactory: 2, c, d show auricles which are oversized and 2 e is rather fanciful regarding the ornamentation. Janira dutemplei D'ORBIGNY is undoubtedly a N. sexcostata; D'ORBIGNY's figures do not correspond to reality; he drew a forma β and his specimens belong to forma α, as can be seen on fiche 43 by ROGER. Janira carantonensis D'ORBIGNY falls into synonymy of N. sexcostata; contrarily to what D'ORBIGNY and J. ROGER wrote (une valve droite... qui correspond parfaitement à la diagnose de D'ORBIGNY...) the specimens from the D'ORBIGNY collections have 4 to 5 intercalary ribs (this can be seen on fig. 1 of ROGER). They correspond with forma β, but their principal ribs are not so very salient. I can see no specific difference between figure 1 of ROGER and figure 6 a, plate 41 in WOODS. Neithea martiniana (manuscript D'ORBIGNY in J. ROGER) is established with very poorly preserved specimens; I do not hesitate to consider them synonyms with N. sexcostala because, also from Martigues, there are several very well preserved N. sexcostata specimens in the collections of the Kat. Univ. Leuven. Neithea (Neithea) matsumotoi sp. nov. I. HAYAMI, 1965 (pp. 297-299, pt. 41, figs. 1-7) does not seem to be different from N. sexcostata, despite what I. HAYAMI says; as far as can be judged from description and figures only, no difference can be found; but N. matsumotoi is stratigraphically earlier than N. sexcostata and, because of that, it seems preferable not to draw conclusions without having seen the material. In the Prodrome D'ORBIGNY described a Janira albensis from various Lower Cretaceous localities. The lectotype figured by J. ROGER on fiche 40 is very fragmentary. The part which is left shows a nice rib-section which could belong to N. sexcostata. The very incomplete state of the sole specimen makes it impossible to draw a conclusion.» DHONDT, A. V. 1973. Systematic revision of the subfamily Neitheinae (Pectinidae, Bivavia, Mollusca) of the European Cretaceus. Mémoires du Institute Royal des Sciences Naturelles de Belgique, 176: 1-101, pls. 1-5. [p. 46]
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Neithea (Neithea) sexcostata (S. Woodward, 1833); A. V. Dhondt, 1973, Systematic revision of the subfamily Neitheinae of the European Cretaceus, plate 5, figures 2a, 2b.
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