Vertipecten Grant & Gale, 1931
GRANT IV, U. S. & H. R. GALE. 1931. Catalogue of the marine Pliocene and Pleistocene Mollusca of California and adjacent regions. Memoirs of the San Diego Society of Natural History, 1: 1-1036, pls. 1-32, text figs. 1-15. [p. 188]
«Subgenus VERTIPECTEN, new subgenus
Type: Pecten nevadanus Conrad (+ Pecten bowersi Arnold).
Shell fairly thick, usually large; strengthened with large radial ribs which are somewhat irregular in number and prominence, showing a tendency to bifurcate or multiply by intercalation, often roughened by imbrication; left valve usually strongly convex, right valve nearly flat; ears on large specimens strengthened by riblets and sometimes imbricated, the riglit ventral ear being elongate and narrow, separated from the ventral sub-margin by a large byssal notch which leaves behind it a scar as wide as the ear, the ventral submargin strongly concave, the dorsal nearly straight; interior of hinge practically smooth, except for a shallow cartilage pit.
Geologic range: Eocene to middle Miocene (California and Oregon).
The type of this group and its two varieties fucanus Dall and perrini Arnold have several distinctive characters which clearly separate them from the groups to which they have formerly been assigned. P. nevadanus and variety perrini have been called Lyropecten because of their large heavy shells. The smaller northern variety, on the other hand, was assigned to Chlamys; and a more than usually regular specimen of nevadanus was assigned to Patinopecten under the name of kernensis Hertlein. The relationship with Patinopecten is the closest, and it is possible that it may be found more convenient to consider Vertipecten merely as the ancestral section of Patinopecten. However, the size and coarseness of the shells, the irregularity and imbrication of the ribs, and the greater convexity of the left valve compared with the nearly flat condition of the right valve make it seem hardly appropriate to class this peculiar group with Patinopecten. Vertipecten is probably derived, like Lyropecten, from Chlamys; but it is not otherwise related to Lyropecten, and the heaviness of the shell gives the two but a superficial resemblance. The irregularity and imbrication of the ribs, the tendency of some of the ribs on the left valve to stand out above the others, and the shape of the elongate right ventral ear, which has an unusually large byssal notch with a scar behind it as broad as the ear, shows the close relationship with Chlamys; but again the size and coarseness of the shells, and the unequal convexity of the valves (the right valve, instead of the left as in Janira, being nearly flat), and the prominence of the ribs distinguish Vertipecten.
Vertipecten appears to be the connecting link between Chlamys and Patinopecten. Unlike Lyropecten, it seems to have been a native of the Pacific coast in the Oligocene. Before the upper Miocene, it gives place to the Patinopectens, and apparently there are no living representatives which have retained its distinctive characters.
It is possible that this subgenus has already received a name in one or more of the New Zealand or Australian publications;¹ but, as is characteristic of the work of the modern school of conchologists in that region, new names are given in such profusion, usually without explanations, references or figures, that it is not worth the effort to try to keep up with them. The present writers do not feel able to identify Phialopecten, although the description sounds very much like that of Vertipecten. It would, of course, be a matter of very great interest if it should be discovered that Vertipecten is the same as Phialopecten and that the forms of unknown origin that appeared in the Pliocene of New Zealand really came from the Eocene and Miocene group that split off from Chlamys in California. One case like this of migration between California and Australia would, if proven, show that the route between the two places is navigable by at least some kinds of marine mollusks; and such a case would be a blow to the New Zealand and Australian provincialists, as well as to the Californian.»
¹Cf., for instance, "Genus" Phialopecten Marwick, Trans. New Zealand Institute, Vol. 58, p. 454, 1927, type (by original designation) Pecten triphooki Zittel, Novara Expedition, Geologischer Theil. Vol. 1, Pt. 2, p. 52, pl. 9. fig. 4, 1864. Zittel's figure seems to indicate that Phialopecten is quite distinct from Vertipecten but the writers have not seen an actual specimen of Zittel's species.»
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Pecten (Vertipecten) nevadanus Conrad; U. S. Grant IV & H. R. Gale, 1931, Catalogue of the marine Pliocene and Pleistocene Mollusca of California and adjacent regions, plate 7, figures 2a-2c.
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Vertipecten bowersi (Arnold); J. T. Smith, 1991, Cenozoic Giant Pectinids from California and the Tertiary Caribbean Province. plate 32, figures 4, 5.
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«Vertipecten Grant and Gale, 1931
Type species (original designation): Pecten nevadanus Conrad (+ Pecten bowersi Arnold) [ = Pecten bowersi Arnold, 1906; see taxonomic comments under Vertipecten bowersi].
Diagnosis.-- Valves equal in height and length in most species, but height exceeds length in the youngest taxon. Profiles variable, from equally convex to planoconvex right valves and strongly convex left valves. Ribs or costae and interspaces numerous, of varying widths, with imbricated or scaly fine sculpture in most taxa. Shagreen or screenlike microsculpture preserved in some species. Rib profiles vary with time (see table 5). Auricles equal, with scaly radial riblets. Byssal notch deep; hinge area smooth, lacking crura. Vertipecten differs from Lyropecten and "Macrochlamis" in valve profiles, scaliness of ribs and auricles, hinge, and byssal area; ribs and costae are irregularly spaced. Vertipecten has the deep byssal notch of Chlamys but differs from it in having more equal auricles, no hinge crura, coarser imbricated sculpture, and unequal valve profiles, a planar left valve and convex right valve.»
SMITH, J. T. 1991. Cenozoic Giant Pectinids from California and the Tertiary Caribbean Province: Lyropecten, "Macrochlamis", Vertipecten, and Nodipecten species. United States Geological Survey Professional Paper, 1391: v + 1-155, figs. 1-18, pls. 1-38. {p. 76]
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