Vertipecten kernensis (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, pls. 3-4. [p. 40, pl. 4, fig. 3]
L. G. Hertlein, 1925, plate 4.
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«Shell large, slightly arched, moderately thick. Right valve ornamented by about 22 to 24 fairly high, flatfish topped, round edged, radiating ribs of unequal size, separated by slightly rounded interspaces which are narrower than the ribs, many of the interspaces sculptured by a tiny midrib, whole surface ornamented by fine concentric lines of growth; anterior ear large, bearing a large byssal notch, ear ornamented by about 4 or 5 radiating riblets crossed by concentric lines of growth; posterior ear ornamented by about 6 radiating riblets crossed by concentric lines of growth. Height approximately 93 mm.; length approximatley 93 mm.; length of hinge line 57 mm.; apical angle approximately 100º.
Type: Right valve. No. 128 (L. S. J. U. Type collection), from Loc. 150 (L. S. J. U.) Pyramid Hill, 3 miles northwest of mouth of Kern River Canyon, Kern County, California; W. D. Kleinpell collector. Monterey, Miocene. Pecten kernensis differs from P. propatulus Conrad, and P. oregonensis Howe, in the more numerous, unequal ribs, and less numerous, coarser ribs on the posterior ear of the present species. From P. caurinus Gould, P. kernensis is distinguished by the narrower ribs and strongly sculptured ears. A species very similar to or identical with P. kernensis has been reported from the Miocene of Lincoln County, Oregon, by H. V. Howe.» LEO GEORGE HERTLEIN, 1925
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«Holotype.— LSJU 128, a right valve 9.3 cm high, 9.3 cm long. An excellent specimen showing diagnostic characters of both valves is hypotype USNM 647085 (pl. 2, fig. 7, pl. 36. fig. 4).
Type locality.— Pyramid Hill, Kern County, northeast of Bakersfield, Calif., (LSJU loc. 150). Rio Bravo Ranch 7½-minute quadrangle, sec. 14, T. 28 S., R. 29 E. Rocks mapped as the "Freeman Silt-Jewett Sand, undifferentiated" unit (Bartow and Doukas, 1976). Miocene. Toxonomic comment.— Vertipecten kernensis (Hertlein) is the oldest valid name for the taxon known as V. nevadanus Conrad of authors. For 75 years it was assumed that the external mold described by Conrad as Pecten nevadanus from Ocoya (now Poso) Creek was the same as the well-preserved form occurring in abundance in basal ledges at Pyramid Hill several miles to the southeast. Subsequent stratigraphic and systematic studies distinguished an older Vertipecten in the undivided Freeman Silt and Jewett Sand unit at Pyramid Hill and two younger species, V. fucanus and V. bowersi, in the overlying Olcese Sand that crops out to the north of Poso Creek. Conrad's name probably referred to one of the younger species (see discussion under V. bowersi) and the next available name for V. nevadanus auctt. is V. kernensis (Hertlein). Pecten gabbi Clark, 1918 (a homonym renamed P. diabloensis Clark by Hanna, 1924) from the Diablo Range of northern California, is probably the same species. It is known from a few poorly preserved specimens that lack the detailed locality and biostratigraphic data of V. kernensis. Description.— Right valves flat to slightly convex, left valves convex. Height and length nearly equal. Auricles equal, radially ribbed; byssal notch deep. Hinge line greater than half shell length. Umbonal angle 98-108º, varying with convexity. Right valves with 21-23 narrow, rounded ribs, some furrowed and some incipient. Leftvalves with 17-19 narrower, higher ribs that vary in width, prominence, and spacing. One to three ribs may be more prominent imbricated key ribs, as in V. fucanus. Fine flanges commonly preserved on anterior- and posteriormost ribs, auricles and interspace riblets. Left valves generally scalier than right valves, interspaces having 2-4 scaly riblets that complicate accurate rib counts. Adults range as much as 15.4 cm high, 15.8 cm long, 7.5 cm hinge length (LACMIP loc. 462), and one slightly deformed individual measured 18 cm high, 15 cm long (USGS loc. M2826, from the La Panza Range). Variability.— Rib profiles are higher, more rectangular in juveniles, lower in adults. State of preservation affects microsculpture, especially the shagreen pattern in interspaces. There is some evidence that stratigraphically higher specimens (for example, hypotype UCMP 36554) have two prominent key ribs on left valves and a slightly lower rib count (17-18) than in stratigraphically lower specimens (for example, hypotype USNM 647085, left valve 19-20). Comparative morphology.— Stratigraphic successions of Vertipectens trace the gradual evolution of V. perrini to V. kernensis, intermediate forms being referable to either species. Right valves are hard to distinguish but left valve proportions, rib counts, and fine macrosculpture separate end members of the series. Morphologic differences and evolutionary trends in California Vertipectens are summarized in table 5. Phylogenetic affinities.— Vertipecten kernensis is intermediate in morphologic characters and Stratigraphic occurrence between V. perrini and V. bowersi. It is probably the immediate ancestor of V. fucanus. Morphologically similar late Eocene or early Oligocene species from the Pacific Northwest include V. popofensis MacNeil, 1967 from an unnamed formation equivalent to the Acila shumardi zone in the Shumagin Islands (USGS 3563, 5037) and Chichagof Bay (USGS 3373), and from the Tokun Formation in the Katalla district, Alaska (USGS 4323). Vertipecten porterensis (Weaver) from the Lincoln Formation of Weaver (1912) (= Lincoln Creek Formation (Moore, 1976) and V. columbianum (Clark and Arnold) from the Sooke Formation, Vancouver Island, may also be closely related. Geographic and Stratigraphic distribution.— Northern California, from the Diablo Range and the Santa Lucia Mountains, including the type locality of the Vaqueros Formation; Pyramid Hill area, Kern County; San Emigdio Range, southern San Joaquin Valley; Santa Ana Mountains, Orange County. Morphologic links between V. perrini and V. kernensis are found in the Santa Lucia Range. Representative occurrences.— San Lorenzo Series of Clark (1918), Mount Diablo Range, type specimens of Pecten gabbi Clark (UCMP loc. 1311). Vaqueros Formation, Junipero Serra 15-minute quadrangle, southern Coast Ranges. Los Vaqueros Valley and east of Vaqueros Creek, type section, members E, F of Thorup (1943): LSJU 2412; LSJU 2411, specimens tectonically deformed, misidentified on old labels as Pecten perrini; CAS 31524. Adelaida 15-minute quadrangle, southern Santa Lucia Mountains; the Lepidocyclina (L.) californica locality of Schenck and Childs (1942). Vertipectens from here (LSJU 1155) are intermediate between V. kernensis and V. perrini. Agua Sandstone Bed, Santos Shale Member, Temblor Formation, Temblor Range: LSJU 2862, USGS M2631. Poorly preserved fragments of a form transitional between V. perrini and V. kernensis are found with "Macrochlamis" magnolia ojaiensis. Painted Rock Sandstone Member, Vaqueros Formation, La Panza Range: M2826, in lower of two Crepidula biostromes. Monterey Formation, near base of the Saltos Shale Member, northwest Caliente Range; Chimineas Ranch 7½-minute quadrangle, from Crepidula-Antigona bed (M3781). Vaqueros Formation, Santa Susana Mountains (LSJU accession no. 22358, from Oak Ridge, east of Grimes Canyon, Ventura County). Vaqueros Formation, Painted Rock Sandstone Member, Sierra Madre Range, (Fritsche, 1969). Fox Mountain quadrangle, near head of Olive Canyon; specimens technically distorted (UCLA 5539) and abundant (UCLA 5545). Undivided Freeman Silt and Jewett Sand, Pyramid Hill area, Kern County. Rio Bravo Ranch, Knob Hill, and Pine Mountain 7½-minute quadrangles. At Pyramid Hill, basal part of the Jewett Sand (M1591), friable sandstone with concretions, including "grit zone" of Addicott (1970b). The species was abundant in ledges along the southwest flank of Pyramid Hill (sees. 14, 15, T. 28 S., R. 29 E.), but by the mid-1970's localities were essentially quarried out by avid collectors. LACMIP 462, large lots of articulated specimens representing juveniles to adults; M5211, lowest Stratigraphic occurrence, in the Pyramid Hill Sand Member of the Jewett Sand. In basal part of the Jewett Sand at GAS 69; M1590, M1591; UCMP B-1662, UCR 1149, all large lots from the southwest side of Pyramid Hill. LSJU accession no. 2945 from "top of Pyramid Hill Sand." Hypotype UCMP 36554 (pi. 33, figs. 1,5) is an evolutionarily advanced form from UCMP B-1673, about 40 ft above base of the Jewett Sand (Addicott, 1965). UCMP B-1656, from Knob Hill 7½-minute quadrangle, is near the top of a lower sandy facies of the undivided Freeman Silt and Jewett Sand unit, 230-240 ft stratigraphically above its base (Addicott, 1965). An Ostrea-Pecten biostrome in concretionary silty sandstone has evolutionarily advanced forms with fewer ribs and a better developed left-valve key rib. Fossils are very scarce in this area, leached and poorly preserved. Vaqueros Formation, upper member, from upper Sespe Creek (CSUN 263); V. kernensis occurs with "Macrochlamis" magnolia ojaiensis at its highest stratigraphic position. San Lorenzo Formation, Mount Diablo Range (UCMP 1311), type locality of Pecten (Lyropecten) gabbi Clark, 1918. Pleito Formation, San Emigdio Mountains, southern San Joaquin Valley, USGS 4448; M3750, from Balanus-Vertipecten reef in Pleito Hills quadrangle, 150 ft stratigraphically below base of basalt; USGS loc. M3751. Vaqueros Formation, Santa Ana Mountains, Orange County: AMNH collection, material from E. W. Warth, good specimens with no further locality data; LACMIP 1373, Santa Ana Canyon, "Topanga Formation" of label. Geologic age.— Late Oligocene to early early Miocene. Biostratigraphic data.— Index species of the middle "Vaqueros" Stage. Found with "Macrochlamis" magnolia ojaiensis, n. subsp., in the Upper Sespe Creek area and near Pyramid Hill, Kern County, Calif.» 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. 81, 82, 84]
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Vertipecten kernensis (Hertlein, 1925); J. T. Smith, 1991, Cenozoic Giant Pectinids from California and the Tertiary Caribbean Province. From up to down: plate 2, figures 6, 7; plate 32, figure 3; plate 33, figures 1, 5, 6; plate 36, figures 1-5.
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