Argopecten abietis abietis (Jordan and Hertlein, 1926)
JORDAN, E. K. & L. G. HERTLEIN. 1926. Expedition to the Revillagigedo Islands, Mexico, in 1925, IV. A Pliocene Fauna from María Madre Island, Mexico. Proceedings of the California Academy of Ciences [4th Series], 15 (4): 209-217, pl. 23. [p. 214, pl. 23, figs. 1, 3 & 7]
1926 Pecten (Plagioctenium) abietis Jordan and Hertlein, 1926
E. K. Jordan and L. G. Hertlein, 1926, plate 23.
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«Shell averaging about 45 millimeters in altitude, about as long as high, fairly thick and solid, somewhat produced posteriorly. Right valve ornamented by 19 - 21 subtriangular ribs, in adults becoming flattened toward the margin, separated by sharp, narrow-bottomed interspaces, the sides of the ribs and interspaces decorated by sharp, close-set fringing lamellae; hinge line about two-thirds the length of disk ; ears about equal in length, rather large, the anterior ear ornamented by about four rather faint radial ribs crossed by concentric lines of growth, the byssal notch well defined; posterior ear faintly radially and concentrically sculptured. Left valve with the ribs more pronouncedly triangular in cross-section, the sides densely fringed with lamellae; ears similar to those of right valve, but the byssal notch on anterior ear less developed; hinge strong; cardinal crura well developed. Altitude 45 mm.; longitude 46 mm.; diameter of left valve about 32 mm.; apical angle about 100°.
Type: Left valve. No. 2079, paratypes Nos. 2080, 2081, 2082, and 2083, Mus. Calif. Acad. Sci., from Loc. 937 (C.A.S. coll.), Arroyo Hondo, Maria Madre Island, Mexico; upper Pliocene; Hanna & Jordan, collectors. This species is closely related to P. circularis, but is distinguisliable by the character of the ribbing. The ribs of P. abietis are wide at the base, and are triangular or subtriangular in cross-section. The interspaces are very narrow, and the sides of the ribs and interspaces are covered by a dense fringe of concentric lamellae. The ribs of P. circularis are distinctly rounder and much narrower in cross section, and the interspaces are much wider. Examination of a large series of specimens from Maria Madre Island, where this species is very abundant, and also from various localities in the upper Pliocene of the Gulf of California region, shows the angularity of the ribs to be a constant characteristic. The writers realize that intergradation with P. circularis proper may ultimately be proved, but as yet the present species is known only from the subtropical Pliocene. The name (abietis,─ of the fir) refers to the dense fringes of lamellae, like needles of a conifer». ERIC KNIGHT JORDAN & LEO GEORGE HERTLEIN, 1926
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«REMARKS: The byssalnotch varies somewhat in depth but is never so deep as in the living Pecten purpuratus or Pecten circularis; further, the anterior ear is not so produced in proportion to its width as in those two species. The ribs normally have a low V-shaped profile, thus differing from the two aforementioned living forms in which the sides of the ribs are nearly vertical.
This species is very abundant in the Arroyo de Gua-Arroyo de Arce area where it is by far the dominant form in thick Pecten reef beds. Over 50 well-preserved specimens from loc. A 3557 were examined. Many more could have easily been collected if there had been facilities for bringing them in from the field. In some well-preserved specimens at loc. A 3524 the byssalnotch is extremely shallow, in others it is of the normal type. Two individuals from loc. A 3555 have much higher ribs than the average. A specimen from loc. A 3559 is 110 mm high, and as heavy as A. hakei (Hertlein), but appears to have the ears of the present species. At loco A 3589 many small specimens have the V-shaped ribs flat-topped, but on the larger individuals these ribs grade into those of the typical form. A few specimens from loc. A 3557 are very close to Pecten mendenhalli Arnold, but the rest are more typical of A. abietis. It is possible that additional collecting at Santa Rosalia (type locality for P. mendenhalli) may show that the two species are the same.» DURHAM, J. W. 1950. Megascopic paleontology and marine stratigraphy. In 1940 E. W. Scripps Cruise to the Gulf of California, Part II. Geological Society of America Memoir 43: 1-216, pls. 1-48. [p. 62]
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Aequipecten abietis (Jordan and Hertlein); J. W. Durham, 1950, Megascopic paleontology and marine stratigraphy, plate 10, figures 4, 7; plate 11, figure 4.
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