Leptopecten ecnomius Woodring, 1982
WOODRING, W. P. 1982. Geology and paleontology of Canal Zone and adjoining parts of Panama. United States Geological Survey Professional Paper, 306-F: 1-759, pls. 83-124. [p. 595, pl. 105, figs. 4-6, 8, 9]
1982 Leptopecten ecnomius Woodring, 1982
W. P. Woodring, 1982, plate 105.
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«Small, height and length subequal, valves of slight to moderate and equal convexity, or left slightly more convex than right, auricles subequal. Valves similarly sculptured. Radial and concentric sculpture appearing at height of 1.5 to 2 mm. Radial sculpture consisting of inverted U-shaped ribs, slightly wider to slightly narrower than interribs; 14 to 17 (generally 16) on right valve, 15 to 17 (generally 16 or 17) on left. Concentric sculpture consisting of fine lamellae; at early stage extending across ribs and interribs, later generally wider and nodelike on ribs, exceptionally continuing like at early stage even to ventral margin. Flanks very narrow. Auricles of immature valves large for size of shell. Radial sculpture stronger on right anterior auricle than on left. Radial sculpture weak or absent on both posterior auricles. Conspicuous concentric lamellae on anterior auricles of some immature valves. Byssal notch deep, moderately wide. Ctenolium long for size of shell. A pair of slender cardinal crura generally well developed. A pair of auricular crura generally present.
Length 22.7 mm, height 21.2 mm, convexity (both valves) 8.2 mm (type). Length 25.7 mm, height 24 mm, convexity about 3 mm (largest specimen). Type (articulated, but valves rotated): USNM 647128. Type locality: 136a (Stanford University 2611, Transisthmian Highway, lat. 9º21' N., plus 1,100 feet (335 m); long, 79º49' W., Panama; same as USGS 16912), lower part of Gatun formation. Leptopecten ecnomius is an abundant and characteristic species of the lower part of the Gatun formation. It is represented by 380 specimens, about equally divided into right and left valves. The range in length is 2.2 to 25.7 mm. Six, including the type, are articulated. The species is very abundant at localities 138c and 138d (actually two collections from the same locality) : almost 300 in the two collections. Even though auricles are missing —as they are on many valves— the long, conspicuous ctenolium serves to distinguish right valves, provided the anterior margin is intact. This species is similar to the living L. bavayi (Dautzenberg, 1900, p. 228, pI. 10, figs. 2, 2a; Greater Antilles, Venezuela, and southward along coast of Brasil), but is larger (length of type of L. bavayi, 10 mm; length of largest specimen in USNM collections, 17.8 mm), and the concentric sculpture is less scabrous. Four names have been proposed for late Miocene and Pliocene forms of Leptopecten from Florida. L. ecnomius is smaller than the form represented in Druid Wilson's large late Miocene collection from Punta Gorda (USGS 22454, length up to 29.5 mm), and its auricles are narrower. Perhaps L. olgensis (Mansfield, 1939, p. 51, pI. 2, figs. 1, 2, 4; proposed as Pecten (Pecten?) wendelli olgensis) is the name to be used for this late Miocene form. The type of Pecten wendelli (Tucker, 1934, p. 612, pI. 25, fig. 1) is unrecognizable. Occurrence: Lower part of Gatun formation (middle Miocene), localities 136a, 137, 137a, 138, 138a, 138b, 138c, 138d, 138e, 138f, 138g, 138h.» WENDELL PHILLIPS WOODRING, 1982
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