Pseudopecten Bayle, 1878
BAYLE, E. 1878. Explication de la carte géologique de France. Tome quatrième, Atlas. Première partie. Fossiles principaux des terrains. Publiée par ordre de M. le Ministre des travaux publics, pls. 1-158. Imprimerie Nationale, Paris. [pl. 121, fig. 1]
«FIG. 1.-- Pseudopecten aequivalvis. SOWERBY, sp. — Individu de taille moyenne, dont les oreillettes ne sont pas bien conservées. On peut cependant en reconnaître la forme d'après la direction des lignes d'accroissement du test.
Lias moyen. Avallon (Yonne).» EMILE BAYLE, 1878
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Pseudopecten aequivalvis. Sowerby, sp.; E. Bayle, 1878, Explication de la carte géologique de France, plate 121, figure 1.
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S. Ros-Franch, A. Márquez-Aliaga & S. E. Damborenea, 2014, Comprehensive database on Induan (Lower Triassic) to Sinemurian (Lower Jurassic) marine bivalve genera and their paleobiogeographic record, figure 36.
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Genus PSEUDOPECTEN Bayle, 1878, explanation pl. 121
Type species.— Pecten equivalvis J. Sowerby, 1816, p. 83.
Remarks.— Although Pseudopecten lacks a ctenolium and should be excluded from the Pectinidae (Damborenea, 2002a), we list it here until it is assigned to another family according to its features.
Stratigraphic range.— Lower Jurassic (Hettangian)–Middle Jurassic (Bajocian) (Johnson, 1984). Cox and others (1969) distinguished two subgenera within Pseudopecten: P. (Pseudopecten) and P. (Echinopecten) Brasil, 1895. Both were reported from Hettangian beds. However, following Johnson (1984), we regard P. (Pseudopecten) as Hettangian and P. (Echinopecten) as Toarcian. Therefore, only P. (Pseudopecten) is included in our study interval.
Paleogeographic distribution.— western Tethys (Fig. 36). During our study interval, Pseudopecten was only distributed in the western Tethys, but from the Pliensbachian onward, it was also reported from South America (Damborenea, 2002a) and Australia (Grant-Mackie, 1994). In addition, Damborenea (2002a) suggested that its presence in the Early Jurassic of Japan and Siberia is also possible.
Tethys domain: Early Jurassic: Hettangian of Spain (Liu, 1995), France, Italy, and Germany (Johnson, 1984); Sinemurian of Spain, Portugal, and Morocco (Liu, 1995), England (Johnson, 1984; Liu, 1995), Italy, France, and Germany (Johnson, 1984). Paleoautoecology.— B, E, S, Un, FaM; R-Sw. Species attributed to P. (Pseudopecten) had a byssal gape at juvenile stages, but it disappeared in adult stages; they lived byssate when young but were later recliners on the substrate, and they could swim actively (see Johnson, 1984, for a complete interpretation of the various species).
Mineralogy.— Bimineralic (Carter, 1990b, p. 388). Outer shell layer: calcite (prismatic + foliated). Inner shell layer: aragonite (cross-lamellar).
ROS-FRANCH, S., A. MÁRQUEZ-ALIAGA & S. E. DAMBORENEA. 2014. Comprehensive database on Induan (Lower Triassic) to Sinemurian (Lower Jurassic) marine bivalve genera and their paleobiogeographic record. Paleontological Contributions, 8: 3-219, figs. 1-61. [p. 101, 102]
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Pseudopecten (Pseudopecten) equivalvis (J. Sowerby 1816); A. L. A. Johnson, 1984, The palaeobiology of the bivalve families Pectinidae and Propeamussiidae in the Jurassic of Europe, plate 2, figures 1, 2, 4-10.
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Genus PSEUDOPECTEN Bayle 1878
Type species. M; BAYLE 1878, pl. 21 [sic], fig. 1; Pecten equivalvis J. SOWERBY 1816, p. 83, pl. 136, fig. 1; U. Pliensbachian, Avallon, E. Paris Basin.
AMENDED DIAGNOSIS
Nearly equivalve to clearly inequivalve; between 12 and 27 radial plicae which are nearly smooth or with spines on RV. L. Jur.-M. Jur., Eu., N. and S. Am., E. Indies.
D1SCUSSION
In his diagnosis HERTLEIN (1969: N372) stated that Pseudopecten was nearly equivalve; Ps. (Echinopecten) barbatus is, however, distinctly inequivalve. HERTLEIN stated that about 15 or 16 plicae were present; text fig. 43 shows that there is at least a ränge between 12 and 27 plicae. Hertlein excluded N. America from the geographic ränge; the latter continent can now be included on the basis of the results of work presented herein.
JOHNSON, A. L. A. 1984. The palaeobiology of the bivalve families Pectinidae and Propeamussiidae in the Jurassic of Europe. Zitteliana, 11: 1-235, pls. 1-11. [p. 60]
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