Leopecten sericeus (Hinds, 1845)
HINDS, R. B. 1844-1845. The zoology of the Voyage of H.M.S. Sulphur, under the command of Capt. Sir E. Belcher, during 1836-1843. Vol. II. Mollusca. Smith Elder and Co. London, 72 pp. [p. 60, pl. 17, fig. 1]
1845 Pecten sericeus Hinds, 1845
R. B. Hinds, 1844-1845, plate 17.
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«Testa, orbiculari, plano-subconvexa, asquiauriculata, velutina, valva sinistra planulata, prope umbonem subconcava, fusca, costis viginti-quatuor, lateribus ad angulum planulatis, cum interstitiis velutinis; valva dextra subconvexa, pallida, costis consimilibus, interdum subgeminis; auriculis sequalibus, rectis, velutinis, plicis duabus obsolelis; intus alba.
Inhab. Bay of Panama. In fifty-three fathoms, on a muddy floor. A single specimen only was obtained.» RICHARD BRINSLEY HINDS, 1845
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«Node 8 represents the onset of a distinctive rib profile on the right valve that is shared by L. sericeus and L. cocosensis. These ribs are low and rounded in transverse profile but have a narrow, raised keel that gives them a somewhat trigonal aspect (Figs. 2.11, 4.7). Both species have very shallow byssal notches, that of L. cocosensis becoming obsolete in late ontogeny.
Leopecten sericeus (Node 9) is unique among extant Leopecten in having whitish zigzag pigment lines on the left valve limited to the crests of plicae and absent from the interspaces. The left valve of this species is almost flat in dorsoventral profile, having less of an ontogenetic change from early concave to later convex curvature. Leopecten sericeus was questionably identified by Pilsbry and Olsson (1941, p. 55) from the Canoa Formation of Ecuador. The right valve that was illustrated by these authors has the trigonal, keeled ribs characteristic of this species, and a large left-valve fragment that was collected by Olsson but not figured (USNM 486260) has trigonal ribs and is concave throughout ontogeny. The benthic and planktonic foraminifera of the Canoa Formation indicate that this unit is no older than the late Late Pliocene, or about 2.2 million years (Whittaker, 1988, p. 25; Bianucci et al., 1997, p. 290; see zonation and time scale of Berggren et al., 1995, fig. 6).» 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, figs. 1-9. [p. 938]
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Leopecten sericeus (Hinds, 1845); T. R. Waller, 2007, The evolutionary and geographic origins on the endemic Pectinidae of the Galápagos Islands, figures 4.5-4.8.
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«Additional description: Shell nearly orbicular and rather compressed. Average adult specimen 70 mm in height and 75 in length; hinge line less than half length of disk. Right valve gently convex; 22 or 23 ribs, rounded in juvenile stage but usually sharply angled in adult; infrequently rather flat on top and with one or two grooves or a single ridge; interspaces somewhat wider than ribs; minute concentric lamellae covering disk, but often worn off tops of ribs; auricles equal, rather small for size of disk, gently convex, with oblique margins, and covered with minute concentric lamellae. Left valve nearly flat; central portion of disk usually shallowly concave, but occasionally slightly convex; ribs narrow and rounded in juvenile stage, usually becoming rather sharply angled later; interspaces wide, very infrequently with a low riblet near ventral margin; auricles gently concave and with two or three weak ridges; minute concentric lamellae covering disk and auricles. Right valve white, yellow-white or pale brown; left valve yellow-white, yellow, orange-yellow, brown or red-brown, with both lighter and darker blotches and streaks.
Additional descriptive notes: Several adolescent specimens from Cocos Island, Costa Rica, were examined and found to differ in being more compressed, slightly higher than long (rather than the reverse) and having a shorter hinge line. No doubt adult spcrimens are relatively the same, but the author feels that the distinctions are not sufficiently important to merit subspecific rank for this localized form. Geographical Range: Angel de la Guarda Island, Gulf of California, to La Plata Island, Ecuador; Galapagos Islands. Previous records indicated Santa Inez Bay, Gulf of California, to be the northern limit, and Panama Bay the southern. Hancock expeditions collections increased the northern limit by about 480 miles, the southern by about 500, and established the first Galapagos Islands record. Geochronological range: Known only from the Recent. Bathymetric range: Recorded in 7 to 85 fathoms. Ecological data: Usually found in mud or sand bottoms, occasionally rock; associated with nullipores, calcareous algae, coralline and coral.» GRAU, G. 1959. Pectinidae of the eastern Pacific. Allan Hancock Pacific Expeditions, 23: i-viii, 1-308, 57 pls. University of Southern California Press. Los Angeles, California. [p. 141, 142]
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Pecten sericeus Hinds 1845; G. Grau, 1959, Pectinidae of the eastern Pacific, plates 50, 51.
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«The shell of. P. sericeus resembles that of. P. diegensis Dall. The right valve is usually somewhat less brightly colored than the left. The ribs on the right valve are somewhat lower and broader and separated by slightiy wider interspaces than those of P. diegensis Dall. Young specimens of the two species are very similar. The development of stronger, narrower and more squarish ribs, crossed by sharp, concentric, raised lines, appears to take place earlier on the right valve of P. diegensis than on P. sericeus. According to Reeve, the ribs on the large left valve of the type specimen of P. sericeus are sharply triangular. The specimens of P. sericeus, at hand, are small forms, and the ribs on the left valves are not especially triangular, but they are less prominent and wider spaced than those on P. diegensis. In very large specimens of P. diegensis, the ribs on the left valve show a slight tendency toward a. triangular shape in the later stages of growth.
It seems probable that P. sericeus, a southern species, intergrades with the northern P. diegensis. The single, small valves found at Locs. 23779 (C. A. S.), from Maria Madre fsland, Mexico, ar'd 27223 (C. A. S.), Mazatlan, Mexico, seem referable to P. sericeus rather than to P. diegensis.» HERTLEIN, L. G. 1935. The Templeton Crocker Expedition of the California Academy of Sciences, 1932. The recent Pectinidae. Proceedings of the California Academy of Sciences [4th Series], 21 (25): 301-328, pls. 18-19. [p. 304]
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Pecten (Pecten) sericeus Hinds; L. G. Hertlein, 1935, The Templeton Crocker Expedition of the California Academy of Sciences, plate 18, figures 14, 15.
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