Vertipecten yneziana yneziana (Arnold, 1907)
ARNOLD, R. 1907. New and characteristic species of fossil mollusks from the oil-bearing Tertiary formations of Santa Barbara County, California. Smithsonian Miscellaneous Collections, 50 (4-4): 419-447, pls. 50-58 (Published December 13, 1907). [p. 426, pl. 50, fig. 4; pl. 51, figs. 6a-b]
1907 Pecten (Chlamys?) yneziana Arnold, 1907
R. Arnold, 1907, plates 50, 51.
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«DESCRIPTION.—Shell averaging 60 to 70 millimeters in altitude; slightly higher than long, moderately convex, practically equivalve and equilateral, rather thin; base regularly rounded; dorsal margins concave; margins somewhat serrate. Surface of disk onamented by from 30 to 45 irregular, inequidistant rounded, more or less imbricated ribs; in some instances the ribs occur quite regularly, every alternate one being prominent, with lesser ones (appearing as intercalaries) between; in others the ribs are irregularly disposed, although there is a tendency for the alternate ones to be larger and sometimes dichotomous. Ears radially striate in addition to incremental imbricating sculpture; anterior ear of right valve with deep byssal notch and well isolated byssal area.
DIMENSIONS.— Latitude (restored) 75 mm. NOTES.— The imperfect fragments which furnish the characters described above represent a species apparently allied to P. perrini Arnold, although it is smaller and has more numerous and less imbricate ribs than the latter. P. yneziana is the only species of this group found in the Eocene. It has been recognized in the Tejon formation throughout the whole length of the Santa Ynez Range, and as far east as the Ojai Valley, Ventura County. TYPE.— Cat. No. 165,313, U. S. N. M. paratype, same number. LOCALITY.— San Julian ranch, 10 miles southeast of Lompoc, Santa Barbara County, California; locality No. 4507. HORIZON.— Tejon formation, Eocene.» RALPH ARNOLD, 1907
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«Holotype.— USNM 165313, an incomplete right valve 6.4 cm high (Arnold, 1907, gave restored height as 7.5 cm).
Paratypes.— USNM 165313, an incomplete right valve with auricles, byssal area, 5 cm high (incomplete), hinge line 2.5 cm. USNM 165313, juvenile left-valve fragment, 5.2 cm high. West Coast plastotypes: UCMP 33448, 33449. Type locality.— Santa Ynez Mountains, Santa Barbara County, Calif.; Lompoc 15-minute quadrangle, San Julian Ranch, 10 mi southeast of Lompoc (USGS loc. 4507). Wilson (1954) elaborated, "Locality 4507 is just above the San Julian Ranch House about 1 mi southeast of B.M. 603 [not shown on recent maps, but it is on El Jaro Creek about 0.5 mi southeast of mouth of Ytias Creek]." Arnold (1907) called it the Tejon Formation, Eocene in age, but later maps show it as the Gaviota Formation, late Eocene in age (Dibblee, 1950, pI. 1). Significant hypotypes.— LSJU 9262, two-valved specimen collected by Weaver and Kleinpell (pI. 32, fig. 1).9.7 cm high, 9.8 cm long; LSJU 9263, right-valve fragment showing complete anterior auricle and byssal area (pI. 38, fig. 6). Description.— Valves equally, slightly convex; outlines nearly circular, although adult shells commonly flare anteriorly and posteriorly. Auricles subequal, anterior auricle with three or more radial costae; byssal notch deep. Hinge line shorter than half shell length. Left-valve umbo more convex than right valve; umbonal angle 94-100º in right valves, 880 in left valves. Right valves with 30-40 low rounded ribs that tend to bifurcate in later growth stages. Rib counts complicated by interspace riblets that approach ribs in width and prominence. Widest ribs in center of shell; narrower and scalier ribs near anterior and posterior margins. Left valves with 24-25 or more ribs of equal prominence. The largest individual seen was incomplete, and it measured 9.7 cm high, 9.8 cm long (LSJU 9262). Comparative morphology.— Adults are smaller, fewer ribbed than those of V. perrini. Umbonal angle smaller than in V. perrini, greater than in V. alexclarki. The types of Pecten (Vertipecten) yneziana subyneziana Weaver and Kleinpell (1963) are internal molds of small right valves having 20 or more ribs, but they are not well enough preserved to identify with certainty (pI. 38, fig. 5). Phylogenetic affinities.— This species, oldest of the California Vertipectens, grades into V. alexclarki by the late early Oligocene and into V. perrini by the early late Oligocene. The first link is not well documented, because specimens are rare, but the progression of V. yneziana to V. perrini in the western Transverse Ranges is recorded by a number of transitional forms from intermediate strata. The internal molds serving as types of Pecten yneziana subyneziana are from the undivided Saca.te and Gaviota Formations (UCMP B-6963) or "Coldwater" sandstone of Weaver and Kleinpell (UCMP B-6940). These and other small Paleogene Chlamys, such as those referred by authors to Chlamys sespeensis (Arnold), are possibly ancestral to V. yneziana but they were not considered in this study. Geographic distribution and stratigraphic occurrences.— Western Transverse Ranges, especially Lompoc and Los Olivos 15-minute quadrangles, Santa Ynez Mountains, southern California. Arnold (1907) reported it as far east as Ojai Valley, but this could not be verified from specimens. Santa Ynez Mountains, in canyons cut by south-flowing streams east and west of Gaviota Canyon. Gaviota Formation, middle member (common in friable sandstones near the contact between middle and upper members of the Gaviota Formation, according to Wilson, 1954). Undivided Sacate and Gaviota Formations, (UCMP B-6955); Stanford Summer Geology, 1948; collections by H.J. Hawley; UCMP B-7033. Gaviota Formation, upper part, transitional forms between V. yneziana and V. perrini (UCMP B-7015, juvenile; UCMP A-4646). Geologic age.— Late Eocene to early Oligocene. Biostratigraphic data.— Equivalent to the Refugian Stage. Vertipecten yneziana is neither as abundant nor as widely dispersed as the other Vertipecten index species.» SMITH, J. T. 1991. Cenozoic Giant Pectinids from California and the Tertiary Caribbean Province: Lyropecten, "Macrochlamis", Vertipecten, and Nodipecten species. United States Geological Survey Professional Paper, 1391: v + 1-155, figs. 1-18, pls. 1-38. [p. 86]
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Vertipecten yneziana (Arnold, 1907); J. T. Smith, 1991, Cenozoic Giant Pectinids from California and the Tertiary Caribbean Province, plate 32, figure 1 (above); plate 38, figures 6-8 (below).
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