Neitheidae Sobetsky, 1960
SOBETSKI, S. A. 1960. Contribution to the systematics of the Upper Cretaceous pectinids from the middle part of the Dniester River Basin. Paleontologicheskii Zhurnal, 1960 (2): 63-71.
Neithea quinquecostata of Wade (1926); T. R. Waller, 2006, Phylogeny of families in the Pectinoidea (Mollusca: Bivalvia): importance of the fossil record, figure 9.
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.
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«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, 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]
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