Spondylus scotti Brown & Pilsbry, 1913
BROWN, A. P. & H. A. PILSBRY. 1913. Fauna of the Gatun Formation, Isthmus of Panama. Part 2. Proceedings of the Academy of Natural Sciences of Philadelphia, 64: 509-519, pls. 22-26, text-figs. 1-5 [p. 514, pl. 25, figs. 1, 2]
1913 Spondylus scotti Brown & Pilsbry, 1913
A. P. Brown & H. A. Pilsbry, 1913, plate 25.
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«A species of the S. americanus group, having the lower valve very convex, the upper valve moderately so; beak not much produced. Sculpture of about 17 narrow little-prominent radial ribs, some of them bearing very short, scale-like spines, irregularly placed, and on the lower half only; between these ribs there are fine, unequal longitudinal striae, 4 to 8 in each space. They are crenulated by extremely fine, crowded laminae along the growth-lines. There are some weakly developed foliations on one side of the lower valve.
Breadth 51 mm., length (alt.) of lower valve 65, of upper 58 mm., diam. 41 mm. From the lignitic bed below the Pecten bed at Tower N, Culebra Cut, Well distinguished from the recent Antillean S. americanus Hermann by the delicacy of the sculpture and more convex lower valve. It is also somewhat related to S. gumanomocon⁴ of the Santo Domingo Oligocene, but that is a far more ponderous and long-beaked species.» ⁴ Spondylus gumanomocon n. sp. A species resembling S. varians Sowb. (S. delessertii Chenu). The upper valve is Pectiniform, orbicular, of moderate thickness, with low radial ribs, the principal ones irregularly spinose, spines short; cardinal urea small and short, as in S. americanus. Lower valve very ponderous, with a long, level (not receding) cardinal area, and a very long, straight (or sometimes laterally curved) beak, the cavity of which is deeply excavated in young shells, nearly solidly filled in old ones. Sculpture like the upper valve, except that it is more or less extensively foliated towards the beak.
Length (alt.) of a lower valve 175 mm.; breadth 108 mm.; weight 32½ oz. Santo Domingan Oligocene. This is the form identified by Gabb as Spondylus. AMOS PEASLEE BROWN & HENRY AUGUSTUS PILSBRY, 1913
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«Spondylus scotti Brown and Pilsbry, Acad. Nat. Sci. Philadelphia Proc., v. 64, p. 614, pI. 25, figs. 1, 2, 1913 (Miocene, Canal Zone).
?Spondylus bostrychites Guppy, Cooke, Carnegie Inst. Washington Pub. 291, p. 144, pI. 11, figs. 11a, llb, 1919 (Miocene, Anguilla). ?Spondylus lucasi Maury, New York Acad. Sci., Scientific Survey of Porto Rico and Virgin Islands, v. 3, p. 23, pI. 5, fig. 1, 1920 (Miocene, Puerto Rico). Moderately large, right valve narrowly triangular-ovate to widely triangular-ovate, left valve widely triangular-ovate; moderately inequilateral to almost equilateral; right valve more convex than left. Auricles small. Ribs generally of two orders. Primary ribs generally separated by several very narrow, closely spaced ribs, as many as 12. Primary ribs bearing low vaulted scales or short spines. Very low scales on few secondary ribs of some specimens. Entire shell sculptured with more or less conspicuous fine concentric threads. Umbonal area of right valve generally sculptured also with low foliaceous concentric lamellae. Hinge of right valve, as usual, consisting of a pair of heavy isodont teeth flanking resilium pit. Interior of left valve inaccessible.
Length 52.8 mm, height 67.5 mm, convexity (both valves) 39.5 mm (figured specimen with narrowly triangular-ovate right valve). Length 67 mm, height 78.5 mm, diameter (both valves) 47 mm (figured specimen with widely triangular-ovate right valve).
Type: The articulated specimen illustrated by Brown and Pilsbry, Acad. Nat. Sci. Philadelphia 3863, now lost or misplaced.
Type locality: Lignitic bed below the "Pecten bed" at Tower N [Panama Canal, west side of Las Cascadas Reach], Canal Zone, La Boca formation.
Spondylus scotti occurs in the La Boca formation, including the Emperador limestone member. Eleven right valves, one left, and eight articulated specimens are available, all except four of which are from the La Boca proper. Those from localities 99, 99a, 99f, and 99g were collected in the type area, but not from the same bed as the type.
The range of variation in the outline of right valves is shown by the illustrations. A left valve (locality 100b) is even wider than the wider illustrated right valve and is almost equilateral. The ribs of the wider illustrated right valve show little differentiation as primary and secondary. The ribs of another specimen from the same locality are almost subequal and are almost as narrow as those of S. olssoni. A third specimen from that locality has the prevailing ribbing of S. Scotti. The variation in outline and ribbing is so great that on a typological basis it would be supposed that several species are represented. S. scotti is a representative of a group of species widely distributed in the late Oligocene and Miocene formations of the Caribbean region and Florida. Nine names, but not that many species, are involved. The earliest name (and the only one that antedated S. scotti), S. bifrons, was used by Sowerby (1850, p. 53) for a middle Miocene species from the Dominican Republic. As that name is a junior homonym, Guppy (1867, p. 176) published the substitute name S. bostrychites. This species has been found in the Gurabo formation. The lectotype and five paratypes have been described and illustrated by Palmer (1938, p. 6, pI. 1, fig. 2, pI. 2, figs. 1-3, pI. 3, figs. 1-5). S. scotti is smaller and has more primary ribs. Its secondary ribs are narrower, more numerous, and more closely spaced. Of the specimens of S. scotti in USNM collections, only that shown on plate 97, figures 5, 9, has a full complement of primary ribs: 12 or 13. The type was described as having 17. It is not my intention to consider all the other names. As indicated by the synonymy, however, the small early Miocene Spondylus from Anguilla and that of the same age from Puerto Rico have the basic features of S. scotti. The small species from the late Oligocene of Antigua, listed by Cooke, evidently is the same as that from Anguilla, as he thought. It may be pointed out also that the large specimen, mentioned by Dall when he named S. chipolanus without any illustration (Dall, 1890-1903, p. 759, 1898), and described by Gardner (1926-47, p. 51, 1926), should be designated the lectotype, not the immature specimen (height 29.6 mm) illustrated later by Dall (1915, pI. 19, fig. 1). S. chipolanus is a member of this group from the Chipola formation of Florida. As pointed out by Gardner, contrary to expectation, the immature specimen is from the Chipola formation, not the Tampa limestone. Occurrence: La Boca formation (early Miocene), Gaillard Cut area, localities 99, 99a, 99f, 99g, 99h, 100b, 101b, 101e, 101h, 116a. Emperador limestone member of La Boca formation (early Miocene), Gaillard Cut area, localities 117a, 117b; Madden basin, locality 71.»
WOODRING, W. P. 1982. Geology and paleontology of Canal Zone and adjoining parts of Panama. United States Geological Survey Professional Paper, 306-F: 1-759, pls. 83-124. [p. 601, 602]
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Spondylus scotti Brown and Pilsbry; W. P. Woodring, 1982, Geology and paleontology of Canal Zone and adjoining parts of Panama, plate 97, figures 5, 8-10.
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