Pecten (Pecten) maiquetiensis Weisbord, 1964
WEISBORD, N. E. 1964. Late Cenozoic Pelecypods from Northern Venezuela. Bulletins of American Paleontology, 45 (204): 1-564. [p. 124, pl. 12, figs. 3-6]
«Pecten (Pecten) maiquetiensis, new species PI. 12, figs. 3-6
The description of this species pertains to the left valve.
Left valve slightly concave, suborbicular, a little wider than high. Ventral margin well rounded, dorsal margins slightly concave, sharply shouldered, diverging at an angle of about 83 degrees on young specimens but up to about 107 degrees on adults. Auricles subequal, triangular, the anterior one concave in plan, the posterior nearly plane, squared off straight at the hinge line, and with subtruncate margins. Auricles sculptured by two to four radiating riblets which produce a finely scalloped or serrated effect at the lateral margins, particularly on the posterior ear, and both ears are traversed by numerous sharp sinuous concentric laminae. In the interior, the auricles are raised a little above the level of the disk, and often there is a small nodule or two near the base of the ears, particularly the anterior one. The internal ribs of the left valve are paired crenulations near the basal margin, the crenulations extending upward for but a short distance. The flutings between the ribs at the base proper are deeper than the sulcus dividing the ribs themselves. Muscle scar rather large, more or less orbicular. Chondrophore triangular, the ligamental groove adjacent to the hinge line extremely narrow and rather deep, the area immediately below the groove marked with numerous vermiform striae. Outer surface of disk sculptured by 18 to 20 strong squarish radial ribs separated by interspaces with gently rounded troughs, the interspaces a trifle narrower to a trifle wider than the ribs. The ribs and interspaces are crossed by numerous fine regular concentric laminae and lamellae, the laminae more or less erect on the upper half of the valve but flattening down into lamellae and becoming closer toward the base; the laminae and lamellae, though minutely ragged, run straight across the ribs and interspaces without sinuosity, and are sharper in the interspaces than over the ribs; on the submargins, which are relatively narrow, the concentric lineations are faint and crowded. Dimensions.— Holotype (T329a), left valve, height 34.3 mm.; width 38.2 mm. Paratype (J329a), left valve, height 22.1 mm.; width 22.4 mm. Largest specimen, height 46 mm.; width 52 mm. Type locality.— Upper Mare formation, in stream 250 meters south-southwest of mouth of Quebrada Las Pailas. Two left valves, including the holotype. Other localities.— Lower Mare formation at W-13, on hillside above west bank of Quebrada Mare Abajo. Two left valves. Lower Mare formation, in small stream 100 meters west of Quebrada Mare Abajo. Three left valves, including the paratype. Mare formation at W-14, on hillside above west bank of Quebrada Mare Abajo. Two fragmentary left valves. Comparisons.—The left valve of P. maiquetiensis, n. sp. resembles the left valve of P. bowdenensis Dall (see Woodring, 1925, p. 63, pl. 7, figs. 8-9) and P. barretti Woodring (1925, p. 62, pl. 7, figs. 6-7), both of which are from the middle Miocene Bowden formation of Jamaica. The principal difference between the Cabo Blanco shell and P. bowdenensis is that the intercostals of P. bowdenensis are usually slightly raised whereas those of P. maiquetiensis are not. On P. barretti the auricles have stronger radial riblets than P. maiquetiensis. On the left valve of P. soror (Gabb) (see Pilsbry, 1921, Acad. Nat. Sci. Philadelphia, Proc, vol. 73, p. 410, pl. 44, figs. 1-2) from the middle Miocene of the Dominican Republic there are 17 external ribs and those are rounder, and the interspaces wider, than on P. maiquetiensis. Also the left anterior ear on the type of P. soror does not bear the strong radial riblets of the Venezuelan species. Perhaps the nearest relative of P. maiquetiensis is P. soror urumaconis Harris (1927, Bull. Amer. Paleont., vol. 13, No. 49, p. 22, pl. 13, fig. 1; pl. 14, figs. 3-4) from the Miocene of the State of Falcon, Venezuela, but on the left valve of the Falcon shell both ears are more concave, and the external ribs of the disk more rounded than on the Cabo Blanco shell. The Recent Western Atlantic P. chazaliei Dautzenberg (see Grau, 1955, Nautilus, vol 68, No. 4, pp. 113-115), first collected by the yacht Chazalie in 1896 at Los Testigos Island, Venezuela, and which ranges from Florida to Brazil in 10 to 75 fathoms, is a smaller, more fragile shell than the fossil P. maiquetiensis, and on the left valve the interspaces of P. chazaliei are much wider. P. chazaliei was formerly known as P. tereinus Dall (1925, Nautilus, vol. 38, No. 4, p. 115). Remarks.— It is not precluded that P. maiquetiensis, n. sp. is, in truth, the left valve of P. caribeus, n. sp. (represented by the right valve only), but as neither P. maiquetiensis nor P. caribeus were found with both valves attached, it seems advisable to consider them distinct for the present.» NORMAN EDWARD WEISBORD, 1964
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N. E. Weisbord, 1964, plate 12.
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