Patinopecten healeyi (Arnold, 1906)
ARNOLD, R. 1906. The Tertiary and Quaternary pectens of California. United States Geological Survey Professional Paper, 47: 1-264, pls. 1-53. [p. 103, pl. 36, fig. 1, 1a; pl. 37, figs. 1, 1a, 2]
1878 Pecten expansus Dall, 1878
1906 Pecten (Patinopecten) healeyi Arnold, 1906
1914 Pecten californicus Cossmann & Peyrot, 1914 [nomen novum pro Pecten expansus Dall, 1878]
1978 Pecten (Patinopecten) healeyi sanclementensis Susuki & Stadum, 1978
1906 Pecten (Patinopecten) healeyi Arnold, 1906
1914 Pecten californicus Cossmann & Peyrot, 1914 [nomen novum pro Pecten expansus Dall, 1878]
1978 Pecten (Patinopecten) healeyi sanclementensis Susuki & Stadum, 1978
R. Arnold, 1906, plate 36.
R. Arnold, 1906, plate 37.
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«Description.— Shell averaging about 130 millimeters in altitude, length about equal to height, inequivalve (the right slightly more ventricose than the left), equilateral, and with smooth margins; base evenly rounded; sides only slightly concave above. Right valve somewhat ventricose, and ornamented by 18 to 21 strong, squarish, subequal primary ribs, which become more or less dichotomous, and sometimes trichotomous, after 30 or 40 millimeters in length; medial sulcus of rib more or less deep, in some cases being as deep as the interspaces near the ends, thus completely dividing the primary rib; interspaces subequal, much narrower than the ribs, quite deeply channeled, and often ornamented by a small, rounded intercalary riblet; whole surface crossed by numerous line lines of growth; hinge line less than one-half length of disk; anterior ear only slightly longer than left, arcuate in front, and ornamented by several obsolete radial ridges and numerous sharp incremental lines; byssal notch quite prominent; posterior ear slightly obliquely truncated, and ornamented by sharp incremental lines and sometimes by obsolete radiating ridges. Left valve much compressed; ribs narrow and rounded, more or less sharply toward the top (there being in some cases a narrow, slightly raised line along the top); interspaces wide, and each ornamented by a more or less prominent, rounded, intercalary riblet; whole surface striated concentrically by fine, sharp, wavy lines; ears obliquely truncated and sculptured similarly to those of the right valve.
Dimensions.— Alt. 112 mm.; long. 112 mm.; hinge line .50 mm.; diameter I8 mm. The measurements are of a specimen somewhat below the average in size. A fine specimen from San Gregorio, San Mateo County, measures 180 mm. in altitude. The most variable factors in this species seem to be the depth and width of the medial sulci on the ribs of the right valve, and the prominence of the intercalary riblet in the left. The specimens from San Gregorio and Pescadero, San Mateo County, show, on the average, flatter ribs, more highly developed medial sulci, and intercalary ribs on the left valve that almost equal the primary ones in importance. Specimens from Purisima and Lobitas, which appear to represent a somewhat lower horizon than the San Gregorio and Pescadero beds, are smaller, slightly more convex, and have two or three less ribs. As the forms from both San Diego and San Mateo counties appear to vary through an almost analogous series of mutations, the slight differences enumerated above have not been deemed of even varietal importance. A variety of P. healeyi with 17 ribs is found at Brea Canyon, 4 miles southeast of Newhall, Los Angeles County, associated with the following fauna: Phacoides acutilineatus, P. richthofeni, Dosinia ponderosa {?), Tritonium sp., Conus n. sp. (?), Pomaulax sp., Turritella cooperi, Tellina idae, Neverita recluziana, Trochita filosa, Chione near succincta, Cardium near corbis, Nassa near fossata. This fauna is probably well down in the Pliocene. P. healeyi appears to have a very limited vertical range at the few localities where it is known. In San Mateo County it is found in the Purisima formation, which lies conformably beneath the Merced series, while in San Diego it is very abundant in beds of lower Pliocene age. The great abundance of this species in both the Purisima and San Diego formations may possibly be taken as evidence of their partial contemporaneity. It was with regret that a name so well established in the paleontological literature of the Pacific coast as P. expansus was found to be preoccupied. Since, however, it becomes necessary to rename the species, it is with pleasure that the writer is enabled to dedicate it to Dr. William Healey Dall. RANGE.
Pliocene. Purisima to Pescadero, and Punta Año Nuevo, San Mateo County (J. P. Smith, Arnold); Temescal Canyon, Santa Monica Mountains, Los Angeles County (Rivers); Pacific Beach, San Diego County, (Hemphill, Dall, Arnold, and others); Tia Juana, Mexico (A. W. Greeley); Brea Canyon, 4 miles southeast of Newhall, Los Angeles County (U. S. Nat. Mus.)»
RALPH ARNOLD, 1906
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«Remarks. — This large, rather flat pecten is easily recognized by its flat-topped, medially sulcated radial ribs on the right valve and the rounded ribs with an intercalary in each interspace on the left valve. Pecten healeyi occurs at nearly every locality where fossils are found in the San Diego Formation in and near San Diego, California.
Juvenile specimens are smooth in the early stage but usually radial undulations of the anterior margin begin to form after the shell has attained a height of 3 to 5 mm. Occasionally specimens remain smooth up to a height of 23 mm. The ribs on the right valve, especially those toward the anterior and posterior margins, begin to develop a slight medical sulcus after the shell has attained a height of 10 mm, but such sulcations on the medial ribs are well developed only after a height of 30 to 40 mm has been attained. Occasionally the ribs on large specimens may bear two sulcations which thus divide the major ribs into three small riblets, but such forms, so far as known, have no taxonomic significance. One such right valve with a strong intercalary in each interspace from Pacific Beach in the collections of the San Diego Society of Natural History, is 165 mm high. The largest specimen of Pecten healeyi seen by us is one collected by G. P. Kanakoff from Loc. 107 (LAM), end of Arroyo Drive, San Diego, which is 222 mm long and 195 mm high. The hinge (incomplete) of a portion of a left valve in the same institution collected by Roy L. Moodie at Pacific Beach, is 99 mm long. The shell on lateral areas of the umbonal portion is 6 mm thick. A low, narrow ridge is present on each side of the ligamental pit. The umbonal portion of the interior of many valves is covered with a layer of calcareous material, the weathered surface of which reveals a network of many fine, irregularly arranged plates or cells. Pecten healeyi appears to be a descendent of Pecten lohri Hertlein (295) as mentioned by Arnold. He pointed out that some forms occurring in the Purisima Formation in San Mateo Co. (296), California, appear to be intermediate between Pecten healeyi and Pecten lohri in their respective lowest and highest stratigraphic ranges. The stratigraphic ranges of these two species have been well defined by Woodring in the Santa Maria district, Santa Barbara Co., California. In that district Pecten lohri occurs questionably in diatomaceous strata of uncertain age and in the overlying Todos Santos Claystone and in the Tinaquaic Sandstone, the latter two of early Pliocene age. Overlying these are the Foxen Mudstone and Careaga Sandstone in which Pecten healeyi occurs. These are of approximately middle Pliocene age. Compared to Pecten healeyi, the shell of Pecten lohri is smaller, more convex, has fewer (14 to 16) and coarser ribs on the right valve and it has a longer hinge line. The medial sulcations on the ribs begin nearer the dorsal margin than they do on P. healeyi, and the intercalary ribs are coarser. Pecten healeyi and P. lohri are Pliocene members of a group which includes Pecten propatulus Conrad (297), described from mid-Miocene strata at Astoria, Oregon, and the only slightly different varieties described as P. haywardensis Lutz (298) and P. haywardensis calaverasensis Hall (299) from mid-Miocene strata in central California. Pecten healeyi is quite distinct from P. propatulus and differs in the more numerous and more deeply sulcated ribs on the right valve, finer ribs on the left valve and smaller byssal fasciole beneath the right anterior ear. Pecten oregonensis Howe (300), described from Pliocene beds at Coos Bay, Oregon, is said to differ from P. propatulus in the higher ribs, wider umbonal angle, and in other details. Pecten tryblium Yokoyama (301) from the late Miocene and Pliocene of Japan bears a resemblance to P. healeyi but is longer in proportion to the height, the ribs on the right valve appear to be proportionally narrower and the hinge line is longer. Pecten yamasakii Yokoyama (302) was placed questionably in the synonymy of Pecten healeyi by Grant and Gale, and Kuroda (303) placed it as a subspecies of P. healeyi. The Japanese species is said to possess 19 to 22 tripartite ribs on the medial portion and bipartite ribs on the anterior and posterior portions of the right valve. A subspecies, Pecten yamasakii ninohensis Masuda (304) is another member of the Japanese group. These oriental forms differ sufficiently from the west American fossils to constitute distinct species. They were placed in the genus Kotorapecten by Masuda in 1963. Pecten duplex Cooke (305) described from beds of mid-Tertiary age on the island of Antigua in the Caribbean Sea, was compared by its author with Pecten healeyi. The Caribbean form has medially sulcated ribs on the right valve but it is said to be smaller and the ribs on the left valve are square-topped and bear a shallow medial groove. This latter feature is reminiscent of Pecten yakatagensis Clark (306) which was described from strata of Pliocene age in southeastern Alaska but the two are not closely related. Olsson and Richards assigned the Antiguan fossil to Flabellipecten. The form illustrated by Manning and Ogle under the name of "Pecten oregonensis Howe var." (307) from Boulder Creek near Femdale, California, also has square-topped medially grooved ribs on the left valve. It was described later by MacNeil as Patinopecten (Lituyapecten) falorensis (308). Pecten healeyi is an index fossil of the San Diego horizon, middle Pliocene, of California and northern Lower California. It has been reported from many localities from Femdale, northern California, to Cedros Island and Bahía Tórtolo (Turtle Bay), Lower California, Mexico. Also from Santa Cruz Island, California. This species lived in warm water unlike its northern relative Pecten caurinus Gould which followed it in stratigraphically later Pliocene and Pleistocene beds in California.» HERTLEIN, L. G. & U. S. GRANT IV. 1972. The Geology and Paleontology of the marine Pliocene of San Diego, California (Paleontology: Pelecypoda). Memoirs of the San Diego Society of Natural History, Memoir 2, Part 2b. pp. 143-409, pls. 27-57. [p. 185]
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Pecten (Patinopecten) healeyi Arnold; L. G. Hertlein & U. S. Grant IV, 1972, The Geology and Paleontology of the marine Pliocene of San Diego, California, plate 31, figures 1, 4, 6, 7; plate 33, figure 9; plate 36, figures 8, 9.
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