Yabepecten condoni (Hertlein, 1925)
HERTLEIN, L. G. 1925. New species of marine fossil Mollusca from western North America. Southern California Academy of Sciences Bulletin, 24 (2): 39-46 [p. 41, pl. 4, figs. 8, 9]
L. G. Hertlein, 1925, plate 4.
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«Shell of medium size, subcircular, equivalve, equilateral, somewhat compressed, of moderate thickness. Right valve ornamented by about 16 smooth, faint, radiating ribs which broaden rapidly as the shell becomes larger, at the ventral margin being about two or three times as wide as the very slight interspaces; whole surface of shell ornamented by concentric lines of growth, these in some specimens quite pronounced and in others almost wholly lacking; ears small, obliquely truncated, a very slight byssal notch present on the anterior ear, ears sculptured by numerous fine concentric lines of growth. Left valve slightly more globose at the umbo, sculptured much as right. Interior of valves ribbed. Height 73 mm.; length 73 mm.; hinge line approximately 25 mm. in length; apical angle approximately 105º.
This species is known to attain a size of 85 mm. in height and 90 mm. in length. Type: No. 15 (L.S.J.U. Type collection); Paratype: No. 18 (L.S.J.U. Type collection), from Loc. 148 (L.S.J.U. = N. P. 44), at dam No. 35, West Wishkah River, Washington; H. Hannibal collector, Montesano, Miocene. Pecten condoni is different in appearance from any other Amusium described from the West Coast Tertiary. The Amusiums are probably of Oriental derivation and living species of Amusium are now found in Oriental waters. Pecten condoni Hertlein is associated with, Venerella oregonensis Conrad. This species is named in memory of Dr. Condon, professor of Geology at the University of Oregon. The writer has adopted the manuscript name of Arnold and Hannibal.» LEO GEORGE HERTLEIN, 1925
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«Miyagipecten alaskensis MacNeil. 1967, from the upper Miocene upper part of the Yakataga Formation in south-central Alaska differs [from Yabepecten ogasawarai sp. nov.] in having a smaller shell with more irregular, distinct LV intercalary costae. Masuda and Addicott (1970) tentatively synonymized this species with Yabepecten condoni (Hertein). The nearly smooth RV shell surface and the LV sculptured by fine, stringy radial costae and shagreen microsculpture indicate that M. alaskensis probably belongs in Yabepecten, as was done by Masuda and Addicott (1970), Uozumi et al. (1986a) and Matsubara (1996). The holotype and paratype of M. alaskensis are too fragmentary to evaluate thoroughly, and additional material is needed to determine its precise taxonomic position.»
MATSUBARA, T. 2003. A new Miocene Yabepecten (Bivalvia: Pectinidae) from the Hongô Formation in northeast Japan. Paleontological Research, 7 (2): 167-179, figs. 1-5. [p. 173]
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«Remarks: These morphological characters indicate that this species should be assigned to the genus Yabepecten. Yabepecten condoni is closely related to Y. tokunagai (YOKOYAMA) (Figure 2) from the early Pliocene of northern Japan (MASUDA, 1962, 1963). The right valve can usually be distinguished from Y. tokunagai by its radial ribs, which are always broader than their interspaces; the left valve differs in being moderately inflated. Nevertheless, the right valves of these species are sometimes rather difficult to distinguish from each other.
Miyagipecten saromensis HASIMOTO & KANNO, 1958, from the Miocene Chirai Formation of Hokkaido, Japan, also resembles Yabepecten condoni, but it can be distinguished by the smaller number of radial ribs on the right valve, which are also less distinct, and by the rather distinct ribs provided with intercalary threads on the left valve. Miyagipecten alaskensis MACNEIL, 1967, an early Pliocene species from the upper Yakataga Formation, Malaspina District, Alaska, is doubtfully included with the present species, as indicated by a comparison with the type specimens, both of which are very poorly preserved and fragmental. Type Locality: Loc. No. 148 (Stanford University, NP 244) at dam No. 35, west fork of the Wishkah River, Grays Harbor County, Washington (SE^NW^ sec. 35, T. 21 N., R. 7 W). Upper part of the lower member of the Montesano Formation of FOWLER (1965). Early Pliocene (?).
Age of the Montesano Formation of Fowler (1965): The age and correlation of the Montesano Formation of FOWLER (1965), in terms of the Pacific coast mega-invertebrate chronology (WEAVER et al., 1944), is doubtful because no definitive biostratigraphic study of the formation has ever been made. Although specialists in larger invertebrates include the lowermost part in the late Miocene, they place the bulk of the formation in the early Pliocene because of faunal similarity with the early Pliocene Empire Formation of coastal Oregon (WEAVER, 1945; YOUNGQUIST, 1961; ADDICOTT, 1966). Preliminary study of extensive collections from the Montesano Formation made by Gerald A. Fowler suggests that there is, indeed, a faunal change between assemblages from near the base of the formation and those from stratigraphically higher parts. This change seems to occur stratigraphically below the Yabepecten localities, and for this reason these localities are here tentatively considered to be of early Pliocene age. It is noteworthy that the most recent studies of benthonic Foraminifera from the Montesano Formation (FOWLER, 1965; RAU, 1967) have considered the greater part, or all, of the formation to be of late Miocene age.
KEEN's ( 1954) belief that mollusks from the type locality of Pecten condoni (NP-244) and from a nearby locality (NP-243) were of middle Miocene age seems to have been influenced by reconnaissance mapping by WEAVER (1937) that showed both localities as included in the Astoria Formation. Recent geologic mapping and biostratigraphic studies of this area (FOWLER, 1965; RAU, 1967) show that these localities are in the Montesano Formation and are of post-middle Miocene age. Associated Fauna: The following mollusks occur with Yabepecten condoni at U. S. Geological Survey locality M2991 near the top of the lower part of the Montesano Formation on the middle fork of the Wishkah River, Grays Harbor County, Washington: Calyptraea sp., Fusitriton cf. F. oregonensis (REDFIELD), Cyclocardia sp., and Lucinoma cf. L. acutilineata (CONRAD). The assemblage is suggestive of a cool, shallow-water depositional environment.
Distribution: Upper part of the lower member of the Montesano Formation of FOWLER (1965), western Washington: Stanford Univ. loc. NP 244 and NP 249; USGS loc. M2991 and M3039. Upper part of the Yakataga Formation, southeastern Alaska: USGS loc. M1321(?).»
MASUDA, K. & W. O. ADDICOTT. 1970. On Pecten (Amusium) condoni Hertlein from the west coast of North America. The Veliger, 13 (2): 153-156, figs. 1-9. [p. 154, 155]
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Yabepecten condoni (Hertlein); K. Masuda & W. O. Addicott, 1970, On Pecten (Amusium) condoni Hertlein from the west coast of North America, figures 1, 3-9.
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