Neithea alpina (Orbigny, 1847)
ORBIGNY, A, D'. 1844-1847. Paléontologie francaise. Description des Mollusques Rayonnés fossiles. Terrains crétacés. III. Lamellibranches. 807 p., pls. 237-489. Chez Arthus Bertrand, Libraire-Éditeur. Paris [p. 643, pl. 446, figs. 4-8]
1842 Pecten versicostatus var. (c) Matheron, 1842
1847 Janira alpina Orbigny, 1847
1849 Pecten tricostatus Bayle in Fournel, 1849
1877 Janira doumerci Péron, 1877
1888 Janira ficalhoi Choffat, 1888
1967 Neithea bahianensis Brito, 1967
1847 Janira alpina Orbigny, 1847
1849 Pecten tricostatus Bayle in Fournel, 1849
1877 Janira doumerci Péron, 1877
1888 Janira ficalhoi Choffat, 1888
1967 Neithea bahianensis Brito, 1967
A. d'Orbigny, 1844-1847, plate 446.
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«J. testâ ovatâ, trigonâ, depressâ; valvâ superiore complanatâ; valvâ inferiore convexâ, incurvatâ, radiatlm 6-costatâ; costis rotundatis, elevatis; interstitiis sulcis latis, bicostatis.
Dimensions. Largeur, 53 millim. — Par rapport à la largeur: longueur, 100/100; épaisseur, 36/100. — Angle apicial, sans les oreilles, 85°.
Coquille ovale , trigone, transverse, déprimée. Valve supérieure plane, striée concentriquement et costulée. Valve inférieure bombée, à sommet contourné , pourvue de six grosses côtes rayonnantes, saillantes, arrondies, entre lesquelles sont des sillons très-larges , peu creusés, où l'on remarque deux côtes égales, élevées, plus larges que les sillons qui les séparent. En dehors des grosses côtes externes il n'y a qu'une seule petite côie rayonnante.
Rapports et différences. Rapprochée par son ensemble du J. quinquecostata, cette espèce s'en distingue par sa forme moins bombée, par ses côtes moins saillantes, et surtout par deux petites côtes égales entre chaque grande, au lieu de quatre. L'extérieur des côtes latérales n'a aussi qu'une côte au lit u de sept. Localité. Elle a été recueillie dans la craie chloritée à Escragnolle (Var), par MM. Mouton et Astier. J'en ai sous les yeux plusieurs exemplaires. Explication des figures. Pl. 446, fig. 4. Coquille de grandeur naturelle, vue en dessus. De ma collection. Fig. 5. La même, vue en dessous. Fig. 6. La môme, vue de profil. Fig. 7. Côtes grossies. Fig. 8. Profil des mêmes.» ALCIDE D'ORBIGNY, 1847
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«Brito (1967) discussed the resemblance of his new species N. bahiaensis to N. ficalhoi (Choffat, 1888), the latter now a synonym of N. (N.) alpina, and differentiated them on the basis of the stronger secondary ribs in N. bahiaensis. In that his material is conspecific with our specimens, N. bahiaensis is here considered a junior synonym of N. (N.) alpina.
Hayami (1965, p. 289) discussed the group of N. ficalhoi, including Janira alpina d’Orbigny, 1847, J. ficalhoi Choffat, 1888, N. occidentalis Conrad, 1855, N. georgetownensis Kniker, 1919, Vola irregularis Böse, 1910, V. subalpina Böse, 1910, Pecten texanus Roemer, 1852, and P. tricostatus Bayle, 1849. All these species are very similar and most probably conspecific (Hayami, 1965). In her revision of Neithea, Dhondt (1973) discussed Hayami’s (1965) observations and concluded that there is no reason to separate N. ficalhoi and N. alpina. Dhondt (1973, p. 19) also mentioned N. texana (Roemer), N. subalpina (Böse) and N. irregularis (Böse) from North America as similar to N. alpina. However, the former two differ from the alpina–ficalhoi group by their lack of tripartite principal ribs. These species probably fall within the variability of N. alpina. However, for a definite decision about the synonymy of these species, a revision of the North American faunas is needed. Dhondt (1973) did not mention N. occidentalis Conrad, a species that also belongs to this group of North American taxa. In his original description of that species, Conrad (1855) emphasized the ‘trifid character’ of the principal ribs, which is produced by a raised line or fine rib on the flanks of the principal ribs. In this respect Conrad’s species falls within the concept of N. alpina, as noted by Hayami (1965), who placed it in his N. ficalhoi group. According to Dhondt (personal communication), N. alpina and N. occidentalis are probably distinct species, and the latter a synonym of N. syriaca Conrad, 1852. However, judging from the original descriptions and the discussion by Dhondt (1973), N. syriaca differs from N. alpina by the absence of tripartite principal ribs, its four unequal intercalary ribs, and the smoothness of its areas and auricles.» ANDRADE, E. DE J., J. SEELING, P. BENGSTON & W. SOUZA-LIMA. 2004. The bivalve Neithea from the Cretaceous of Brazil. Journal of South American Earth Sciences, 17: 25-38, figs. 1, 4. [p. 32, 33]
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Neithea (Neithea) alpina (d’Orbigny); E. de J. Andrade et al., 2004, The bivalve Neithea from the Cretaceous of Brazil, figures 4.6-4.12.
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«Differentiation and affinities with other species.— N. alpina characterized by a rib arrangement consisting of six principal ribs with two intercalary ribs in each intercostal interval, and showing on well-preserved specimens concentric striae all over the ribs, holds a fairly isolated position in the Neithea (Neithea) group. Several authors, mainly German, have however published notices of occurrence and descriptions of supposed N. alpina from their Senonian, where in fact N. striatocostata (GOLDFUSS) was concerned. The differentiation between these species is not very difficult: in N. striatocostata the complete shell is covered with radial striae, the ribs are not clearly delimited amongst themselves, and there are four intercalary ribs, of which the nearest to the principal rib can have the appearance of side-ribs. In this case it could be that a poorly preserved specimen or a "Steinkern" gives the impression of having only two intercalary ribs. As long as a portion of the shell is left it is possible to see the radial striae and these are a good character for differentiating N. striatocostata from N. alpina. On Steinkernen it is very difficult to distinguish between the two species, especially if no auricles are present; if they are present then N. striatocostata has small auricles and inwardly curved areas, whereas N. alpina has relatively larger auricles and outwardly curved areas.
It is easy to differentiate N. alpina from other Neithea-species with clearly delimited ribs by considering the number of intercalary ribs: N. gibbosa (PULTENEY), N. regularis (SCHLOTHEIM), N. coquandi (PERON) have three intercalary ribs; the third species is known to occur with one of the intercalaries less developed (var. atropha): the third intercalary is then comparable with the non-detached side-rib resulting from the tripartition of a principal rib of N. alpina. Nevertheless both species can always be differentiated because in N. coquandi the auricles are relatively smaller, the areas are inwardly bent, the U.P.D. is much longer than the W. on the convex valve and the left valve is really concave. N. quinquecostata and N. syriaca have 4 intercalary ribs. The Neithea-species which are characterized by poorly delimited ribs, such as N. notabilis (MUENSTER in GOLDFUSS) and N. atava (ROEMER) can be differentiated from N. alpina on the shape of the ribs. In the North American Cretaceous several species have been described, which judging from their descriptions and figures, appear to be similar to N. alpina: from the Albian-Cenomanian of Mexico and Texas N. texana (ROEMER, 1852), N. subalpina (E. BOESE, 1910), N. irregularis (E. BOESE, 1910). It seems very likely that when American and European material are compared the two first will be found to be synonymous with N. alpina. It is sometimes difficult to differentiate between specimens of N. alpina and of N. hispanica (D'ORBIGNY), particularly if one only has flattened valves of N. alpina on which principal and intercalary ribs have the same development: the differences are then : — the proportion of U.P.D./W.: N. alpina U.P.D. < W., N. hispanica U.P.D. ± = W.; — the number of ribs: 16 for N. alpina, 18-22 for N. hispanica.» 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. 18, 19]
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