Neithea aequicostata (Lamarck, 1819)
LAMARCK, J. B. 1819. Histoire naturelle des animaux sans vertèbres, présentant les caractères généraux et particuliers de ces animaux, leur distribution, leurs classes, leurs familles, leurs genres, et la citation des principales espèces qui s'y rapportent. Tome sixième, Premier partie, 343 p. Chez l'Auteur, au Jardin du Roi. De l'imprimerie de A. Belin. Paris, 1819. [p. 181]
1819 Pecten phaseolus Lamarck, 1819
1819 Pecten aequicostatus Lamarck, 1819
1824 Neithea pectinoides Drouet, 1824
1824 Neithea laevigata Drouet, 1824
1837 Pecten tumidus Dujardin, 1837
1841 Pecten longicollis Roemer, 1841
1897 Vola ettalensis Soehle, 1897
1819 Pecten aequicostatus Lamarck, 1819
1824 Neithea pectinoides Drouet, 1824
1824 Neithea laevigata Drouet, 1824
1837 Pecten tumidus Dujardin, 1837
1841 Pecten longicollis Roemer, 1841
1897 Vola ettalensis Soehle, 1897
G. W. Knorr, 1768-1778, Recueil de monumens des catastrophes, que le globe terrestre a essuiées, contenant des pétrifications et d’autres dessinées, 2, plate B.II.
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«P. testâ inaequivalvi, trigonâ; valvâ superiore planâ; alterâ tumidâ, incurvato-arcuatâ; radiis 28 ad 30 confertis, glabris, aequalibus.
Knorr. Petrif. 2, tab. B. II. nº. 22. f. 3. Habite aux environs du Maus, département de la Sarthe, et près d'Angers. Cabinet de M. Menard et le mien. Espèce remarquable, très voisine de la suivante [Pecten versicostatus Lamarck], dont elle est distincte, et qui devient plus grande. Largeur, 50-52 millimètres.» JEAN BAPTISTE LAMARCK, 1819
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«Material: Interior of a left valve (B182: H =36 mm; L = 35 mm) and incomplete exterior of a left valve (B230), both from Col dei Schiosi.
Remarks: Valve B182 shows about 35 egual ribs, hence its identification.
Discussion: The incomplete specimen (MPUR/ns 23 -17) from Late Cenomanian strata in the Marsica mountains (Abruzzo, central Italy) identified by Sirna in Praturlon and Sirna (1977; see also Carbone et aI., 1981 and Carbone and Sirna, 1981) as Neithea aequicostata has (even when taking into consideration the missing parts) too few ribs to represent this species. It is very probably a specimen of N. (N.) hispanica (d'Orbigny, 1850). The latter taxon, which is close to N. (N.) aequicostata but has fewer ribs (20 against 24 to 35), is frequent in Tethyan outcrops. Therefore, these two species could probably be interpreted as vicariants (Text-fig. 3).
Distribution: Widely distributed in Albian-Cenomanian strata of temperate sea deposits. In Tethys, however, it is rare.»
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. 190]
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Neithea (Neithea) aequicostata (Lamarck, 1819); 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 4, figure 15.
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«Synonymy.— Pecten aequicostatus LAMARCK = Pecten phaseolus LAMARCK.
The similarity is unmistakable: the general shape and the auricle shape are the same; they occur in the same localities and in the same stratigraphical horizons. The "differences" concern the rib-structure and are solely due to the preservation state: well-preserved specimens are recognized as Neithea phaseola; they have smooth shells with shallow grooves that delimit the ribs. If this outer layer is worn away then the shells appear under the condition which has been described as Neithea aequicostata; the shell is covered with equal ribs with not very deep intercostal intervals. How a N. phaseola becomes a N. aequicostata was illustrated, without however his recognizing it, by D'ORBIGNY, 1847 (pl. 444, figs. 7 and 10): the uppermost shell-layer is worn away and the, at first, linear intercostal grooves become deeper and broader and this process continues till the shell is worn away completely: the Steinkern is covered with ribs and intercostal intervals which have the same width. N. pectinoides is assimilated by DROUET himself to Pecten aequicostatus LAMARCK. N. laevigata according to DROUET's figure and description is a perfect duplicate of Pecten phaseolus LAMARCK and thus of N. aequicostata (LAMARCK). Pecten tumidus DUJARDIN is as far as can be judged from the description and figure a well-preserved Neithea aequicostata. Pecten longicollis ROEMER: is a slightly distorted N. aequicostata. D'ORBIGNY's interpretation has given rise to many problems; his Janira phaseola as seen on the figures and in the description is what LAMARCK describes as Pecten aequicostatus. This is the case for the specimens labelled 6464, 6464 A and 6464 B in his collection. 6464 C however is a N. hispanica. In his description and figures of Janira aequicostata a confusion seems to have arisen between N. aequicostata (LAMARCK) and N. quinquecostata (SOWERBY): the specimens labelled 6473, are such that the convex valve (figured by D'ORBIGNY on pl. 445, fig. 1 and by ROGER on figs. 5 and 6) very probably belongs to N. quinquecostata, whereas the flattened valve definitely belongs lo N. aequicostata. In the D'ORBIGNY collection the specimens labelled 6413 A from Villers (Calvados) and 6473 C from Schandau and Bannewitz (Saxony) are definitely N. aequicostata; 6473 B from Escragnolles (Var, laps. cal. is really Alpes Maritimes) is probably a N. hispanica (D'ORBIGNY). 6467 from Irs, near Castellane, is a typical N. aequicostata, but 6467 A from the same locality, which the manuscript D'ORBIGNY-label qualifies as Janira aequistriata, and which J. ROGER has figured on fiche no. 34, figures 8 and 9, is very probably a N. coquandi (PERON). N. ettalensis has been poorly figured by SOEHLE; the specimens which I saw in Munich leave no doubt as to their identity as N. aequicostata. It is possible that what I. HAYAMI, 1965 (pp. 309-310, pl. 43, fig. 6) describes as N. (s.l.) aketoensis sp. nov. from the Albian of Japan is in fact a N. aequicosteta. The figured specimen, which is the only one that has been found so far, is incomplete and does not allow a definite conclusion to be drawn. Variability.— This species is very variable in the number of ribs and in the size of the individual specimens.
Size : In the English Cenomanian all the specimens are of small size, whereas in the other areas where N. aequicostata is found, there is a large variability in the size of the individuals. In some Cenomanian localities such as Hautrage (Hainaut, Belgium), and around Regensburg and Dresden, the proportion of individuals reaching a large size is very high. This is remarkable, because, although such large specimens are found in the type-locality, they are rare. Rib number: In this species it is impossible to differentiate between ribs and areal riblets (these are the ribs on the area-side of the first principal rib). Because of this the number of ribs, which is fairly constant in most Neithea-species, as long as no riblets are taken into account, is highly variable in N. aequicostata. On Steinkernen the areal riblets are no longer visible and so the number of ribs is automatically lower (since this preservation-state is the only one known from several localities those specimens cannot be eliminated). Differentiation.— Neithea aequicostata (LAMARCK) and Neithea hispanica (D'ORBIGNY) are two very similar species. They can only be differentiated by their number of ribs; N. hispanica has only 19-22 ribs. Amongst all other Neithea-species N. aequicostata can easily be recognized by its equal ribs, which make it impossible to differentiate principal from secondary ribs.
Generic attribution.— Pecten aequicostatus LAMARCK being the type-species of Neithea DROUET belongs to the genus by definition and its correct name thus becomes Neithea (Neithea) aequicostata (LAMARCK).»
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. 12, 13]
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Neithea (Neithea) aequicostata (Lamarck); A. V. Dhondt, 1973, Systematic revision of the subfamily Neitheinae of the European Cretaceus, plate 1, figures 1a-1c.
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