Pleuronectites Schlotheim, 1820
SCHLOTHEIM, E. F. VON. 1820. Die Petrefactenkunde auf ihrem jetzigen Standpunkte durch die Beschreibung seiner Sammlung versteinerter und fossiler Überreste des Thier- und Pflanzenreichs der Vorwelt erläutert. lxii, 437 p. Becker'schen Buchhandlung. Gotha, 1820. [p. 217]
Pleuronectites laevigatus; M. Hautmann, 2010, The First scallop, figure 1.
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«Type species
Pleuronectites laevigatus Schlotheim, 1820, by subsequent designation (Fischer 1886). Revised diagnosis
Comparatively large pectinids with procrescent discs; height of valves greater than length; left valve more convex than right valve; shell exterior smooth or with radial ribs; right anterior auricle with auricular scroll and deep byssal notch; ctenolium present; right posterior auricle obtuse but well delimited, not projecting above hinge margin; auricles of left valve lacking auricular sinuses and dorsally levelling with hinge margin; ligament alivincular-alate, small bourrelets may be present; hinge without resilial- and infraresilial teeth; shell interior without buttresses; shell bimineralic, outer shell layer calcitic, thin, with coarse, radially arranged prism-like structures, inner shell layer aragonitic. Other species
More than a dozen species have been assigned to Pleuronectites (Diener 1923, pp. 85–86; Allasinaz 1972, p. 223; Waller 2005, pp. 38–40). Some of these might be synonymous with the type species, as suggested by Waller (2005, p. 39) for Pecten laterestriatus Philippi, 1899 and Pecten schmiederi Giebel, 1856. Other assignments were clearly erroneous (see below) or cannot be verified due to insufficient morphological information. Currently, only the type species can be definitely included in Pleuronectites. Distribution
Anisian-Ladinian; Germany, Hungary, Sardinia, Afghanistan, China Erroneously assigned species
Many species that have been assigned to Pleuronectites do not fulfil the revised diagnosis of Pleuronectites. These unjustified generic assignments have had a detrimental influence on phylogenetic reconstructions, because they have led to taxonomical concepts of Pleuronectites that mixed characters of true Pleuronectites and other genera, particularly entoliids. More specifically, one of the specimens assigned to ‘‘Pleuronectites’’ balatonicus (Bittner, 1901) by Allasinaz (1972) has nicely preserved basal auricular and lateral disk buttresses (Allasinaz 1972, pl. 43, Fig. 6b–c), which are characteristic of entoliids (Waller 2006) but are lacking in Pleuronectites. According to Waller (2005, p. 39), this specimen belongs to Pecten inornatus Stoppani, 1858, which he assigned to the entoliid genus Crenamussium Newton, 1987 [in Newton et al.]. Waller (2005, p. 39) also stated that the morphology of Pleuronectites meeki Newell and Boyd, 1995 suggests an entoliid affinity of this species. However, Waller (2005) was probably similarly misled when he erected ‘‘Pleuronectites’’ newelli Waller, 2005. Typical entoliid characters of this species that are not observed in Pleuronectites include the equilateral disk, the similar convexity of both valves, and a posterior auricle in the left (?) valve that projects distally above the hinge margin. Waller (2005) mentioned the presence of a ctenolium in the right valve, but he did not illustrate this key character. Given the comparatively poor preservation of his material, it appears possible that he was deluded by a fragment of another taxon or by a preservation artefact.» HAUTMANN, M. 2010. The first scallop. Paläontologische Zeitschrift, 84: 317-322, fig. 1. [p. 319, 320]
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