Neithea Drouet, 1824
DROUET, C. 1824. Sur un nouveau genre de coquille de la famille des Arcacées et description d’une nouvelle espèce de Modiole fossile. Mémoires de la Société Linnéenne de Paris, 3: 183-192, pl. 7. [p. 186]
«GENRE,
Coquille libre, inéquivalve, équilatérale, auriculée; valve inférieure concave, terminée par un crochet recourbé en dedans; valve supérieure plane; charnière presque linéaire, multidentée, à dents sériales sur les auricules; deux dents cardinales oblongues, divergentes, aplaties sur les côtés et sillonnées transversalement; fossette du ligament intérieure, insérée sous le sommet.»
(I) De Néith, nom d'une divinité des eaux chez les Gaulois. II y avait dans le lac de Genève un lochcr qui lui était consacré et qui porte encore le nom de Néiton.
CHARLES DROUET, 1824
|
C. Drouet, 1824, Sur un nouveau genre de coquille de la famille des Arcacées et description d’une nouvelle espèce de Modiole fossile, plate 7. Neithea pectinoïdes. N., figures 1, 2; Neithea laevigata. N., figure 3; Neithea versicostata. N., figure 4.
|
Neithea (Neithea?) gibbosa (Pulteney); A. V. Dhondt, 1973, Systematic revision of the subfamily Neitheinae (Pectinidae, Bivavia, Mollusca) of the European Cretaceus, plate 2, figure 3.
T. R. Waller, 2006, Phylogeny of families in the Pectinoidea (Mollusca: Bivalvia): importance of the fossil record, figure 9.
|
«In the Neitheidae (clade 10, Fig. 1), the earliest dissoconch stage has relatively large, acute auricles (Fig. 9; Dhondt, 1973: plate 2, Fig. 3). The anterior margin of the right anterior auricle meets the disk at a slightly acute angle, but there is no differentiated byssal notch, byssal fasciole, or ctenolium. Even at this stage in Neithea, the right valve is already deeply convex and the left valve is flat or concave. During later ontogeny, there is little, if any, ventral migration of the ligament system, and, unlike many members of the family Tosapectinidae, there is no scrolling of the dorsal auricular margins. In very inequivalve species, such as Neithea quinquecostata (Sowerby, 1814), the umbonal cavity of the highly convex right valve remains hollow below the resilifer (Fig. 9A). The dorsal margins of the two valves meet just below the axis of rotation along very narrow, linear zones of apposition that are irregularly crenulated. The resilial teeth of the right valve are basically stand-alone structures that emerge wall-like from deep within the umbonal cavity and extend ventrally well below the ventral margin of the resilifer. Each resilial tooth inserts on the left valve (Fig. 9B), not into a deep cavity on a thickened hinge plate, but rather between a pair of teeth that embrace the resilial tooth. The floor of this socket is raised above the general inner surfaces of the auricles. Although studies of very early ontogeny are still incomplete, true dorsal and infradorsal teeth appear to be absent. In Neithea quinquecostata of Wade (1926), each resilial tooth is capped with a thin, dark grey, homogeneous layer that contrasts with the light-coloured crossed-lamellar aragonite of the remainder of the tooth, and there is a corresponding thin lining that covers the resilial sockets (Fig. 9B). That these layers were present in life is indicated by the presence of transverse corrugations on both teeth and sockets. The dark grey appearance of these capping layers matches that of the outer calcitic layer of the shell and thus suggests that the dental layers are calcitic, but this has not yet been confirmed by a more detailed examination.
The derivation of Neitheidae from Tosapectinidae is problematic because of the extensive time gap between the last tosapectinid in the latest Triassic and the first neitheid in the Lower Cretaceous. Some authors have partially filled this gap by assuming that the Lower Jurassic genus Weyla Böhm, 1922, a highly right-convex pectinoidean, is ancestral to Neithea and Hertlein (1969: N371) even regarded Tosapecten as a subgenus of Weyla. Damborenea (1987: 167) argued for a close relationship between Weyla and Neithea on the basis of similarities in hinge structure and ‘the apparent lack of a ctenolium’ in both genera, and she followed Sobetski (1960) in placing both in the family Neitheidae. I, however, agree with Hayami (1961: 161) and Dhondt (1973: 9), both of whom considered Weyla and Tosapecten to be distinct genera and rejected the idea of their close phylogenetic relationship. Waller (in Waller & Stanley, 2005: 45) discussed a number of morphological characters of Weyla that do not occur in either Tosapecten or Neithea, not the least of which is the presence of a ctenolium in the early ontogeny of Weyla (Fig. 10A, B), indicating that this genus belongs in the Pectinidae. As for hinge structures, Weyla (Weyla) has a unique hinge configuration unlike that of Neithea. In Weyla, a distinct hinge plate is present, and its entire surface is a zone of apposition having transverse vertical ridges that interlock between the two valves (Fig. 10C, D). The ridged areas of the right valve are concave (slightly more deeply concave adjacent to the resilifer), and those of the left valve are correspondingly convex, thus providing tightly interlocking articulation between closed valves. The transverse ridges do not extend into the outerligament grooves, which are not crenulated. In this figured specimen, which is considerably smaller than the specimen of Weyla (Weyla) alata angustecostata figured by Damborenea (1987: Fig. 23), there is no sign of the ‘rudimentary tooth’ on the anterior side of the right resilifer that she labelled in her figure, and her ‘vertically striated lamella’ on the posterior side of the resilifer is, in the smaller specimen figured herein, simply the sharp ventral edge of the hinge plate. In Neithea (Fig. 9A, B), the zones of apposition on the hinge plates are very narrow strips bordering the ventral edge of the ligament groove on each side of the resilifer. The resilial teeth of Neithea begin very early in ontogeny and, at the earliest stage thus far observed, they are not part of these crenulated apposition zones.»
WALLER, T. R. 2006. Phylogeny of families in the Pectinoidea (Mollusca: Bivalvia): importance of the fossil record. Zoological Journal of the Linnean Society, 148: 313-342, figs. 1-12. [p. 329, 330]
|
Neithea (Neithea) aequicostata (Lamarck); A. V. Dhondt, 1973, Systematic revision of the subfamily Neitheinae (Pectinidae, Bivavia, Mollusca) of the European Cretaceus, plate 1, figure 1.
|
«STEWART (1930, p. 115) indicates the correct type-species of the genus Neithea DROUET: the first, valid designation of a type-species is indeed that by CHENU (1862, vol. 2, p. 186, figs. 941-944) who chose Pecten aequicostatus LAMARCK, 1819 as the type-species for Neithea.
The interpretation of F. K. NORTH (1951, p. 233) is invalid from the point of view of nomenclature; he designates Pecten quinquecostatus SOWERBY, 1814 as type-species. Herein he seconds the designations by HERRMANNSEN (1847-1849, vol. 2, p. 110), GRAY (1847, p. 200, n" 741), S. V. WOOD (1861, p. 36) which have date-priority over the designation by CHENU but are nevertheless invalid, because Pecten quinquecostatus SOWERBY was not included in DROUET's original species-list. F. K. NORTH was well aware of this, but gave the following arguments for his interpretation: « . . . STEWART suggested that these designations (1) were invalid on the ground that N. quinquecostata was not in DROUET'S original list. But neither was N. aequicostata, except in synonymy. DROUET's first species was his own N. pectinoides (p. 186, pl. 7, fig. 12) and this is quite clearly LAMARCK's Pecten aequicostatus as has never been contested (1819, p. 181). But DROUET also included in his list N. versicostata (Pecten versicostatus LAMARCK, 1819, p. 181) and this is equally clearly the same as N. quinquecostata (J. SOWERBY, 1814, p. 122, pl. 56, figs. 4-8). Thus N. quinquecostata has exactly the same right as has N. aequicostata to receive the subsequent designation as type and HERRMANNSSEN's designation should be upheld ». Despite these arguments it cannot be denied that DROUET expressly mentioned Pecten aequicostatus, even if only in synonymy, but not Pecten quinquecostatus (2) . Conclusion.
The type-species of the genus Neithea DROUET, 1824 is Pecten aequicostatus LAMARCK, 1819.» (1) By HERRMANNSEN, GRAY, S. V. WOOD designating Pecten quinquecostatus as type-species for Neithea.
(2) The synonymy given by F. K. NORTH for Pecten versicostatus LAMARCK which considers LAMARCK'S species identical with Pecten quinquecostatus seems doubtful — more details can be found below, sub Neithea (Neithea) quinquecostata (SOWERBY). DROUET'S conception of N. versicostata is difficult to interpret from his quoted references:
LAMARCK 1814: is not N. quinquecostata (see below). FAUJAS 1799, pl. 28, fig. 4: this is N. sexcostata (S. WOODWARD, 1833). A. BRONCNIART 1822, pl. 4, fig. 1, a, b: this indeed is a N. quinquecostata (SOWERBY, 1814). The figure given by DROUET himself (pl. 7, fig. 4) is insufficiently clear to permit any decision to be taken. 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. 7]
|
«Type-species.— Pecten versicostatus LAMARCK, 1819 (= Pecten quinquecostatus SOWERBY, 1814), Aptian-Turonian, Western Europe, Africa and India (designated by HERRMANNSEN, 1847).
Remarks.— Neithea is a very characteristic genus of the Pectininae in the Cretaceous. Most species of the genus are pIano-convex in outline and provided with six raised primary radial ribs in addition to many secondary riblets on the right (convex) valve. But Neithea aequicostata (LAMARCK, 1819) and a few other species have numerous radial ribs of a single order of prominence on the whole surface of right valve. N. aequicostata and a few related species to it have been generally considered to constitute a distinct taxonomic group from normal species of Neithea. STEWART (1930), who believed HERRMANNSEN's (1847) type designation of N. quinquecostata to be invalid and CHENU's (1862) designation of N. aequicostata to be the first for the genus, proposed Neitheops (type-species: N. grandicosta GABB, 1869) for the six-ribbed normal species. NORTH (1951, p. 233), however, stated, "STEWART suggested that these (HERRMANNSEN's and GRAY's) designations were invalid on the ground that N. quinquecostata was not cited in DROUET's original list. But neither was N. aequicostata, except in synonymy. DROUET's first species was his own N. pectinoides (p. 186, pI. 7, figs. 1, 2) and this is quite clearly LAMARCK's Pecten aequicostatus, as has never been contested (1819, p. 181). But DROUET also included in his list N. versicostata (Pecten versicostatus LAMARCK, 1819, p. 181), and this is equally the same as N. quinquecostata (SOWERBY, 1814, p. 122, pI. 56, figs. 4-8). Thus N. quinquecostata has exactly the same right as has N. aequicostata to receive the subsequent designation as type, and HERRMANNSEN's designation should be upheld."
I agree with NORTH's opinion, and Neitheops should be accepted as a subjective synonym of Neithea s. str. Neithea seems to have appeared first in the Neocomian, and flourished in the Aptian and Albian over the world except for the boreal province and South America. In western Europe and Africa Upper Cretaceous species are also common, while in other continents the genus appeared to have become almost extinct in the Cenomanian stage. The ancestry of Neithea should be sought in the Jurassic species of the Pectininae, and probably in Lower Jurassic "Vola" alata and allied species to it from South America, for which BOEHM (1920, p. 138) proposed a genus Weyla (type-species: Pecten alatus BUCH, by monotypy). In California similar Lower Jurassic pectinids were called Parapecten by CRICKMAY (1933). However, nothing is known about the Upper Jurassic representative of this lineage which could link Weyla with Neitheea. I agree with DARTEVILLE and FRENEIX (1957, p. 71) and TAMURA (1959) in excluding "Neithea" kotsubu KIMURA, 1951, from the Upper Jurassic of Japan, from true Neithea, because it probably belongs to the Chlamydinae. HAYAMI, I. 1965. Lower Cretaceous marine pelecypods of Japan, part I. Memoirs of the Faculty of Sience, Kyushu University, [Serie D - Geology], 15 (2): 221-349, pls. 27-52. [p. 284, 285]
|