Patinopecten jonesi Kanno, 1971
KANNO, S. 1971. Tertiary molluscan fauna from the Yakataga District and adjacent areas of southern Alaska. Paleontological Society of Japan, Special Papers, 16: 1-154, pls. 1-18. [p. 56, pl. 4, figs. 1-4; pl. 6, figs. 1, 2]
1971 Patinopecten jonesi Kanno, 1971
S. Kanno, 1971, plate 4.
S. Kanno, 1971, plate 6.
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«Description:— Shell large, thick, suborbicular; strongly inequivalved, almost equilateral; dorsal margin weakly concave; no visible ctenolium along margin of byssal notch; both valves with about 25 strong radial ribs. Right valve distinctly convex with strong rather square, undercut radial ribs sculptured with very fine, raised concentric lines which continue across the interspaces; interspaces are round-bottomed and narrower than the width of radial ribs and have no interstitiaIs; anterior ear somewhat produced providing a rather deep byssal gape, and sculptured with distinct growth lines; posterior ear rather small, terminal margin concave. Left valve almost flat, but undulating near the ventral margin; surface lacking microscopic sculpture; radial ribs are rather flat-topped, separated by more gently rounded interspaces than that of the right valve.
Length, 147 mm; height, more than 130 mm; length of hinge line, more than 78 mm on the holotype. Remarks:— This species has not been found outside of the Lare Glacier area in the upper reaches of Little River, where the Yakataga formation is underlain unconformably by the Poul Creek formation. The present species occurs in the lowest part of the Yakataga formation which consists of pebble-bearing gray, medium-grained sandstone. The present new species occurs rather abundantly with valves oriented with the convex-side upward. Associated molluscs include Clinocardium yakatagensis (CLARK) and Crepidula sp. This new species has the characteristic features of the genus Patinopecten DALL (1898). It is inequivalved and has a strongly inflated right valve and an almost flat left one, and distinct radial ribs. However, the right valve is sculptured with microscopic fine, silky concentric threads. This sculpture is rather similar to that of the juvenile left valve of P. (L.) yakatagensis (MACNEIL, 1961, pI. 37, figs. 3, 5). However, the left valve of the present species has almost no sculptures other than radial ribs whereas the subgenus Lituyapecten is characterized by raised, fine concentric growth lines in juvenile specimens and frill-like flanges on the radial ribs. Accordingly, the present new species can not be included in the subgenus Lituyapecten MACNEIL, 1961, or Patinopecten (Patinopecten) DALL, 1898. However, the general features show that it belongs to the genus Patinopecten DALL. The present new species may represent a new subgenus of Patinopecten, although the existing specimens are not sufficient to justify the proposal of a new subgenus at this time. The new specific name is dedicated to Mr. RICHARD, L. JONES, a geologist of the Standard Oil Co., who co-operated in the field and assissted the present writer in collecting the present specimens. Locality:— 81402, gray pebble-bearing, medium-grained sandstone, lowest part of the Yakataga formation. Reg. No. TUE 8420 (holotype); TUE 8421 (paratype).» SABURO KANNO, 1971
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