Leptopecten andersoni subandersoni (Loel & Corey, 1932)
LOEL, W. & W. H. COREY. 1932. The Vaqueros formation, lower Miocene of California I. Paleontology. University of California Publications, Bulletin of the Department of Geological Sciences, 22 (3): 31-410, pls. 4-65 [p. 202, pl. 21, figs. 7, 8]
1932 Pecten (Plagioctenium) andersoni subandersoni Loel & Corey, 1932
W. Loel & W. H. Corey, 1932, plate 21.
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Similar in all characters to P. andersoni Arnold (1906) save that the rib number is only 14 and the margins are less serrate. The ribs are slightly wider than in the typical form. Height, 40 mill.; length, 41 mm.
Pectens of the phylum of P. andersoni Arnold which have been collected from many localities in the Vaqueros horizon have consistently fewer ribs than the typical form which has 17, and fewer than those from all collections examined from the Temblor horizon. Rarely is a specimen found in the Vaqueros with 16 ribs; the average number on hundreds counted is 15, many having but 14 well defined ribs. Some individuals from the Temblor horizon have 16 ribs. Since there is an apparent stratigraphic significance in the rib number in P. andersoni it is thought that this Vaqueros form (including variants in outline and rib character as in the case of P. andersoni Arnold) should be given a subspecific or varietal designation. It should be noted that the type of P. andersoni Arnold (1906) was found in sandstones a few feet below the Monterey shale of Santa Cruz County, according to Arnold, and is therefore Temblor in age, in accord with the Temblor faunule associated.
Pecten (Plagiocteniurn) andersoni (Arnold) subandersoni, n. var. is the earliest of an important phylum of Pecten in the Miocene. It is apparently ancestral to P. andersoni Arnold and its Temblor varieties one of which, as suggested by Arnold (1906), is possibly a precursor to P. discus Arnold (1907a) (18-21 ribs). A general increase in rib number is indicated in this group, as in the ease of the Lyropectens (P. magnolia, P. crassicardo, and P. estrellanus). Geologic range.― Vaqueros horizon, Lower Miocene, possibly to Temblor, Middle Miocene. Distribution in Vaqueros.― Near Purisima Nueva, Lower Califomia (Univ. Calif. loc. A599); San Joaquin Hills, Orange County, abundant at Malibu Canyon, Santa Monica Mountains, Los Angeles County; South Mountain, Ventura County; and western Santa Ynez Mountains, Santa Barbara County; very abundant in basal Miocene on the southeast flank of Santa Lucia Mountains from San Luis Obispo quadrangle across southwest corner of Paso Robles quadrangle to west central Adelaida quadrangle, Monterey County. Reported from the Santa Cruz Mountains.» WAYNE LOEL & WILLIAM HENRY COREY, 1932
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