Delectopecten maddreni MacNeil, 1967
MACNEIL, F. S. 1967. Cenozoic pectinids of Alaska, Iceland, and other nothern regions. United States Geological Survey Professional Paper, 553: 1-57, pls. 1-25. [p. 5, pl. 4, fig. 5; pl. 5, fig. 5]
1967 Delectopecten maddreni MacNeil, 1967
F. S. MacNeil, 1967, plate 5.
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«Description.— Shell small; disc has faint concentric growth lines and four or five crude concentric undulations; no radial sculpture. Anterior ear of right valve has 11 or 12 fine radial riblets; posterior ear unknown. Anterior ear of left valve slightly convex along its anterior border, the border nearly vertical; posterior ear smaller, the posterior border sloping at about 45º, weakly concave.
Discussion.—This species is closely related to Delectopecten peckhami (Gabb) as that species was interpreted by Arnold. (See Moore, 1963, p. 67.) The available figures of D. peckhami show about 4 to 6 riblets on the anterior ear of the right valve, whereas D. maddreni has 11 or 12 riblets. The California Academy of Sciences has some specimens identified as D. pedroanus (Trask) that have 10 to 12 riblets on the anterior ear. The distinction between D. peckhami and D. pedroanus is not clear, and some authors (Grant and Gale, 1931, p. 236) have combined them; certainly the type of D. pedroanus came from much younger beds than the type of D. peckhami According to Moore (1963, p. 67), the California occurrences of D. peckhami are all Miocene. Masuda (1962a, p. 164) recorded D. peckhami from late Oligocene to early Pliocene beds in Japan, and Slodkewitsch (1938, p. 113) gave a similar range for the species in Kamchatka. Delectopecten maddreni occurs in beds that are probably of late Oligocene age. It is of about the same age, therefore, as the oldest of the Asiatic forms assigned to D. peckhami, and possibly these Asiatic Oligocene forms are closer to D. maddreni than to D. peckhami. D. maddreni appears to be more closely related to D. peckhami and D. pedroanus than to D. lillisi (Hertlein) (1934, p. 5, pl. 1, fig. 1, pl. 2, figs. 2, 3) from the Kreyenhagen Shale (late Eocene and early Oligocene) of California. D. lillisi has about 10 fine spinose riblets on the anterior part of the disc of the right valve. An apparently undescribed species of Delectopecten occurs in the lower part of the Moreno Formation (Late Cretaceous and Paleocene?) of California (the horizon probably of Maestrictian age). Types: The holotype (USNM 644865) consists of a right and a left valve which may or may not belong to the same individual; the slab on which they occur has many specimens close together. The right valve has a height and length of about 22 mm. A figured specimen from the Poul Creek Formation is numbered USNM 644866. Type locality: Upper part of the Burls Creek Shale Member of the Katalla Formation (horizon probably upper Oligocene), Burls Creek, Katalla district, Alaska, USGS 4321. Locality of figured specimen: Middle part of the Poul Creek Formation (horizon probably upper Oligocene), north end of spur projecting into Bering Glacier, about due north of the mouth of Kulthieth River, Yakataga district, Alaska USGS 16898.» FRANCIS STEARNS MACNEIL, 1967
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