Veprichlamys incantata (Hertlein, 1972)
HERTLEIN, L. G. 1972. Description of a new species of Chlamys from the Galapagos Islands. Proceedings of the California Academy of Sciences, 39: 1-6. [p. 2, figs. 1-5]
1972 Chlamys (Chlamys) incantata Hertlein, 1972
L. G. Hertlein, 1972, figures 1-5.
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«DIAGNOSIS. A species of Chlamys differing from other west American species in possessing very narrow, compressed, rather low, spinose ribs.
DESCRIPTION. Shell averaging about 45 mm. in height, ovate, valves gently and nearly equally inflated, hinge line rather short. Right valve sculptured with about 25 major ribs which are narrow, compressed, rather low, and occasionally unequally spaced; on top of each of these ribs is a row of spines which are concave ventrally; submargins with 5 or 6 very fine riblets; interspaces vary in width but are much wider than the ribs, nearly flat-bottomed, and sculptured with 1 to 3 fine radial threads, each bearing a row of spines, the ribs and interspaces crossed by fine concentric imbricating lines of growth; auricles unequal, the anterior one the larger, sculptured with about 5 spiny radial riblets, the hinge line above the auricle with scaly sculpture, below the auricle a well developed byssal notch about half the length of the auricle, below this along the margin there are 4 pectinidial teeth; posterior ear short, slightly concave, sloping rather steeply downward, sculptured with about 6 radial riblets. Left valve sculptured similar to the right but lacking a byssal notch. Hinge with one pair of slight cardinal crura. fnterior of valves lightly grooved corresponding to the external ribbing. Color of the exterior of the valves whitish, the spines rosy, lending a roseate appearance to the valves, more pronounced on the left one. DIMENSIONS. Length 40 mm., height 45 mm., length of hinge line 21 mm., convexity (both valves together) approximately 13 mm. The largest specimen, a left valve, is 48 mm. high. TYPE MATERIAL. Holotype no. 52263, also paratypes, San Diego Society of Natural History, from off Academy Bay, Santa Cruz (Indefatigable) Island, Galápagos Islands; dredged in 200 meters: Mrs. Jacqueline DeRoy collector, July 25, 1969. Paratypes are deposited in the California Academy of Sciences, the American Museum of Natural History, and in the United States National Museum. COMMENTS. The shape, spinose sculpture, and rosy coloration of this newspecies are somewhat similar to those of Chlamys hastata Sowerby (see Arnold, 1906, pl. 42, figs. 1, 1a, 2, 2a; Grau,1959, plates 27, 28) from California, but the ribs are more numerous, lower, more compressed, and not arranged in pairs on the right valve. The fewer ribs (25) on the new species serve to separate it from Chlamys amandi Hertlein (1935, p. 305; Pecten australis Philippi, 1845, p. 56 ,"Patriae: Insulae Chonos."; not Pecten australis Sowerby, 1842) from Chile, which has 30 to 34 ribs which are only slightly scaly toward the submargins. The sculpture of C. incantata, new species, bears a general resemblance to that of the species described as Pecten (Chlamys) coccymelus by Dall (1898, p. 741, pl.34, fig. 1) from strata of middle Miocene age at Plum Point Maryland. Dall called attention to the similarity of the fossil form to juvenile Pecten madisonius Say, but believed it to be a distinct species. Mansfield (1936, p. 177) stated that it "may be an immature specimen representing a varietal form of P. madisonius," and Rowland (1936, p. 1008) suggested that it "may be a case of arrested development." The sculpture of the new species described here bears a general similarity to that of illustrations of Pecten (Chlamys) nympha Bavay (1906, p. 246, pl. 7, figs. 3 and 4) . The type specimen of that species was described as only about 15 mm. high. The type locality was given as "Habitat Caribaeum Mare?". The type specimen in the Muséum National d'Histoire Naturelle de Paris, was originally in a carton which also contained a specimen of Pecten antillarum Récluz, a typical inhabitant of Caribbean waters. Dr. Thomas R. Waller (written communication, December 30, 1969), who has given considerable time to a study of the Pectinidae of the western Atlantic, stated that he feels certain that Pecten (Chlamys) nympha is a synonym of Chlamys benedicti Verrill and Bush (in Verrill, 1897, p. 74; not Pecten benedicti Lamarck, 1819) described from "off Martha's Vineyard, 1356 fath., dead; West Indies, in 25 to 72 fath., living." Adult specimens of C. benedicti (Weisbord, 1964, pl. 14, figs. 8-11) are quite distinct from the new species described here from the Galápagos Islands. The specific name of this new species, "incantata," is derived from the vernacular appellation, "Las Islas Encantadas" (the Enchanted Islands), sometimes applied to the Galápagos Islands.» LEO GEORGE HERTLEIN, 1972
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«Veprichlamys incantata (Fig. 9.1–9.3) was discovered in 1969 in dredge hauls from a depth of 200 m off Academy Bay, Santa Cruz (Indefatigable) Island (Hertlein, 1972). The collection consisted of six specimens, all paired valves, four of which contained soft parts and were alive when collected. Two of these paratypes are now in the National Museum of Natural History (USNM 770267). Two additional specimens, both paired valves, have since been added to the USNM collections, both from a depth of 200 m off Santa Cruz Island. Although the species is considered to be rare, it is unknown whether this rarity represents low abundance or simply the bias of past collecting in waters shallower than the depth range of the species. As noted by Hertlein (1972), this species is unique to the Galápagos, there being no similar species known from the eastern Pacific. Compared to other Recent species of Veprichlamys, V. incantata is set apart by its more numerous fine secondary ribs that begin to be introduced earlier in ontogeny, before a shell height of 10 mm is reached.
Phylogeny.— Waller (1993, p. 236), in a study of the evolutionary origins of tropical American ‘‘Chlamys’’ in both the western Atlantic and eastern Pacific, reported a fossil species closely related to extant ‘‘C.’’ incantata. This species is C. onzola Olsson, 1964, from the early Pliocene Esmeraldas Formation of Ecuador. (See preceding section on Leopecten regarding the age of the Esmeraldas Formation.) The fossil species is known only from the types, a single left valve (USNM 644085, holotype, Fig. 9.5) and an incomplete right valve (USNM 644086, Fig. 9.4), but the shell morphology of these specimens is instructive. The numbers of primary ribs fall within the range of the extant Galápagos species, and the Ecuadorian fossils share the sharp scales and distinctive microsculptural pattern of other species of Veprichlamys. The fossils differ from V. incantata, however, in having more numerous scaly secondary ribs that are introduced earlier in ontogeny. The Esmeraldas fauna is thought to have lived in deep water at depths exceeding 200 m (Hasson and Fischer, 1986). The stem group for Veprichlamys is probably within a group of chlamydiform pectinids with highly variable sculpture in the Oligocene to Middle Miocene of the Patagonian region of Argentina, this group only recently having become better understood both taxonomically and biostratigraphically (Beu, 1995; del Río, 2000b, 2004a, and references therein). In this group, Zygochlamys geminata (Sowerby I, 1846) is the most similar to V. onzola in shape and ribbing pattern (cf. del Río, 2004b, fig. 9.5) but retains, in at least some individuals in population samples, vestiges of plesiomorphic shagreen microsculpture (Waller, 1993) and lacks the characteristic Veprichlamys microsculpture. Zygochlamys geminata also has the longest stratigraphic range, Oligocene to early Middle Miocene, of any of the Patagonian fossil species (del Río, 2004b, fig. 15). It may also be the stem group for other species groups now living in the southern oceans, namely the recent Z. patagonica-delicatula species group (Beu, 1995, p. 13) and the genus Talochlamys Iredale, 1929. If the stem group for Veprichlamys is correctly identified, then the dense ribbing state of the Ecuadorian Pliocene fossil species, V. onzola, is primitive relative to the less dense state in V. incantata, which in turn is less derived than the sparser, more open ribbing patterns of extant Indo-Pacific species. This phylogenetic order is indirectly corroborated by the fact that, so far as known, Veprichlamys has a fossil record in South America but not in the western Pacific region. The timing of the origin of V. incantata is not tightly constrained because of the rarity of fossils and uncertainty of the true stratigraphic range of the early Pliocene fossil species from Ecuador. Veprichlamys incantata is thus far unknown from the fossil record of the Galápagos, perhaps because its deepwater habitat is unrepresented in Pliocene and later deposits. It would seem likely, however, that the Galápagos species originated during the Pliocene and that the western Pacific evolutionary radiation of Veprichlamys was primarily a Pliocene and Pleistocene event. Implications.— Unlike the Galápagos species from shallower depths discussed above, V. incantata is a member of a clade that has been distinctly Pacific since its origin. If one were to depend only on the extant species of Veprichlamys for phylogenetic inference, it would be tempting to conclude that the Galápagos species evolved from western Pacific ancestors, the morphological innovation being an increase in ribbing complexity as indicated by the increase in secondary ribs. The presence of a single fossil from the early Pliocene of Ecuador, however, suggests just the opposite and allows the Galápagos species to be tied with a stem group that flourished in the Patagonian region in the Oligocene and early Miocene. The evolutionary radiation of the Veprichlamys clade thus appears to be from the Patagonian region into the western Pacific, possibly by an eastward route that followed the direction of Antarctic circumpolar currents (see Beu, 1985, regarding the Miocene origin and dispersal of the Z. patagonica-delicatula species group). The evolution of a longer planktotrophic larval stage, as represented by the larger larval shells of the three Pacific species, may have facilitated this dispersal.» WALLER, T. R. 2007. The evolutionary and geographic origins on the endemic Pectinidae (Mollusca: Bivalvia) of the Galápagos Islands. Journal of Paleontology, 81 (5): 929–950. [p. 943, 944]
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Veprichlamys incantata (Hertlein, 1972); T. R. Waller, 2007, The evolutionary and geographic origins on the endemic Pectinidae of the Galápagos Islands, figures 9.1-9.3.
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