Spathochlamys vestalis (Reeve, 1853)
REEVE, L. A. 1852-1853. Monograph of the genus Pecten. In: Conchologia Iconica, Or Illustrations of the Shells of Molluscous Animals , vol. 8. London [unnumbered pages], 35 pls. [pl. 33, fig. 154]
L. A. Reeve, 1853, plate 33.
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«PECTEN VESTALIS. Pect. testa subtrigono-ovata, paululum altiore quam longa, depresso-convexa, aequilaterali, subaequivalvi, valvis, dextra subconvexiore, costis octodecim radiatis, costis triangularibus, confertis, lira serrato-squamata ad summitatem et in sulco interstitiali; rubescente, punctis roseis aspersa, ad umbones lutescente; auriculis valde inaequalibus.
THE VESTAL PECTEN. Shell somewhat triangularly ovate, a little higher than long, depressly convex, equilateral, nearly equivalve, valves, the right rather the more convex, rayed with eighteen ribs, ribs triangular, close-set, with a serrately squamate ridge along the summit and in the interstitial groove; reddish, sprinkled with rose dots, yellowish at the umboes; ears very unequal. Hab. West Indies. Of a delicate blush-red colour, peculiarly angle-ribbed and serrated.» LOVELL AUGUSTUS REEVE, 1853
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«Comparison.— Spathochlamys vestalis differs from both S. benedicti and S. vaginula in having a more asymmetric hinge line, with the anterior outer ligament much longer than the posterior one. The AOL/POL ratio in specimens greater than 12 mm in shell height is generally above 2.05 in S. vestalis and is commonly in the range of 2.2 to 2.7. In S. benedicti the AOL/POL ratio is generally less than 2.0 and commonly in the range of 1.8 to 1.9. The posterior auricles of S. vestalis compared to S. benedicti are not only smaller relative to the anterior auricles, but they also are more oblique with a straighter, more inclined posterior margin. This difference in posterior auricular obliquity increases with ontogeny. The secondary rib-flank costae, one on each side of each major rib in the central region of the disk, generally appear earlier in S. vestalis than in the other species although there is considerable overlap in time of appearance with that in S. benedicti. The medial costae on the right valve of S. vestalis generally begin later in ontogeny than in S. benedicti. In S. vestalis these costae seldom originate before a shell height of 3 mm is reached; in S. benedicti the origination point is generally at shell heights ranging from 1.5 to 2.5 mm.
Hertlein (1935: 309) compared his new species, Pecten (Chlamys) lowei (= P. vestalis), to several fossil species. These fossil taxa, however, are not closely related, and most are now known to belong to the tribe Aequipectinini. This is also true for Chlamys corteziana Durham, 1950 (see also Moore, 1984:. B22), which Durham (1950, p. 64) thought resembled C. lowei. C. onzola Olsson, 1964, thought by Olsson (1964: 35) to be "probably closest to C. lowei (Hertlein)", is also not closely related. I examined the holotype of Olsson's species and found that it is more closely related to the extant eastern Pacific C. incantata Hertlein, 1972, of the Galápagos Islands. Hertlein (1972) thought that this Galápagos species "bears a general similarity to that of illustrations of P. (Chlamys) nympha Bavay", a species that is now known to be a junior synonym of Spathochlamys benedicti (see above). Sculptural details of both C. onzola and C. incantata, however, indicate that these species both belong in Veprichlamys Iredale, 1929, an Indo-Pacific genus that can be placed in the tribe Chlamydini on the basis of its pre-radial microsculpture and lack of internal rib carinae. Living habits.— The total depth range of live Spathochlamys vestalis, based on specimen data in the USNM collection, is from 9 to 183 m, with most specimens having been dredged between 40 and 90 m. Grau (1959) and Bernard (1983) listed depths as shallow as one and two meters, but such shallow occurrences do not appear to be common for living specimens. There do not appear to be any significant differences in the depth preferences of the two morphs described above nor among different parts of the geographic range of the species. Bernard (1983) gave the sea-bottom temperature range of the species as 10 to 29°C. Data on substrate preference and living position are few. Grau (1959: 93) concluded that the species occurs on "rocky, sandy or muddy bottoms, associated with algae, kelp, bryozoa, coral, coralline and sponge." The only specimens in the USNM collections with the bottom type indicated as mud were collected as dead valves. Some specimens show nearly total cover by thin encrusting sponge, and the persistent byssal notch suggests persistent byssal attachment. Geographic range.— From Santa Catalina Island, California (USNM 774180) southward to Isla La Plata, Ecuador (1° 16' S. Lat.; USNM 774194), in Gulf of California as far north as Bahia San Felipe (USNM 774189), and in the Galápagos Islands (Grau, 1959: 92). Stratigraphic range.— Upper? Miocene to Recent. The Upper Miocene limit is based on the occur rence of this species in the Imperial Formation of southern California (Powell, 1986, 1988), discussed below.» WALLER, T. R. 1993. The evolution of Chlamys (Mollusca: Bivalvia: Pectinidae) in the tropical western Atlantic and eastern Pacific. American Malacological Bulletin, 10 (2): 195-249, figs. 1-14. [p. 236, 237]
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Spathochlamys vestalis (Reeve, 1853); T. R. Waller, 1993, The evolution of Chlamys, figures 10 l-r.
Spathochlamys vestalis (Reeve, 1853), Galápagos morph; T. R. Waller, 1993, The evolution of Chlamys, figures 11 a, b.
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