Mimachlamys canalis (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. [p. 511, pl. 24, fig. 3]
1913 Pecten oxygonum canalis Brown & Pilsbry, 1913
1920 Pecten hodgii Hubbard, 1920
1920 Pecten hodgii Hubbard, 1920
A. P. Brown & H. A. Pilsbry, 1913, plate 24.
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«We refer to this subspecies a series of scallops from the Pecten bed at Tower N, Culebra Cut, Canal Zone, which agree with the Costa Rican P. o. optimum in the main, but differ by having the radial striae almost equal, without an enlarged one on the ridge of each rib. The number of ribs is the same as in optimum. The figured specimen measures, alt. 45.5, length 44 mm. Some are larger, up to 55 mm. in length.
This is a very abundant and characteristic fossil of the upper bed of hard limestone near Tower N. The shells cannot be extricated from the rock, in which they are exposed by breaking it up. While this Pecten is obviously close to Costa Rican and Haitian forms, it seems advisable to signalize the minor differences of the races by subspecific names.» AMOS PEASLEE BROWN & HENRY AUGUSTUS PILSBRY, 1913
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«Woodring (1982: 591) regarded Aequipecten canalis (Brown & Pilsbry, 1913) of the upper Lower Miocene La Boca Formation of Panama as another early member of his strongly scabrous group. Based on an examination of USNM material identified by Woodring, this is unlikely. Aequipecten canalis in early ontogeny has a Chlamys-like form with unequal auricles and posterior auricular margins more or less perpendicular to the hinge, slightly acute, or slightly obtuse, but without a significant posterior sinus, and the posterior auricles are definitely not pointed as in Lindapecten (Woodring, 1982: pl. 97, figs 4, 7; Pl. 10, Fig. 1). Furthermore, commarginals in interspaces are absent throughout ontogeny, there being instead a coarse antimarginal microsculpture present in interspaces and on disk flanks that is more like that present in chlamydinine scallops, particularly Mimachlamys. Scales begin in early ontogeny as tiny, narrow protuberances restricted to the centers of rib crests, unlike the more prominent transverse early scales in Lindapecten, and the first secondary costae to appear on either side of the central row of scales are well separated from the central row. Lastly, although hinges are not preserved or not exposed on most of the specimens from Panama, one of Woodring's hypotypes (USNM 647215) possesses an exposed right posterior hinge that has a well-developed intermediate tooth (Pl. 10, Fig. 1), a feature not observed on any Lindapecten species, the right hinge of which is dominated by strong, laterally extended resilial teeth. Aequipecten canalis closely resembles the Eocene-Recent genus Mimachlamys (see Waller, 1993: 229) in shape, rib pattern, and microsculpture, and I refer the species to that genus.
Mimachlamys canalis in Panama is apparently restricted to the La Boca Formation. Although Woodring (1982: 592) reported the species from the stratigraphically higher Alhajuela Formation (Middle Miocene, stratigraphically below the Gatun Formation), examination of all of Woodring's specimens from the Alhajuela established that they are Lindapecten buchivacoanus falconensis (F. & H. Hodson in Hodson et al., 1927). The specimen that Smith (1991a: figs 3e, g) identified as "Aequipecten canalis" from the middle Miocene Isidro Formation of Baja California Sur, Mexico, is also Lindapecten b. falconensis.» WALLER, T. R. 2011. Neogene Paleontology of the Northern Dominican Republic. 24. Propeamussiidae and Pectinidae (Mollusca: Bivalvia: Pectinoidea) of the Cibao Valley. Bulletins of American Paleontology, 381: 1-197, pls. 1-18. [p. 81]
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Mimachlamys canalis (Brown & Pilsbry, 1913); T. R. Waller, 2011, Neogene Paleontology of the Northern Dominican Republic. 24. Propeamussiidae and Pectinidae, pl. 10, fig. 1
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«Of medium size, height and length subequal, valves of equal convexity or left slightly more convex than right, auricles subequal. Sculptured with 17 to 20 arched primary ribs (generally 18 or 19), generally wider than interribs, exceptionally of about same width. Low blunt scales or nodes appearing on ribs of well-preserved shells at height of 3 to 6 mm. Fine secondary riblets appearing on ribs and interribs at height of about 10 mm or later, or not at all, even at height as great as 40 mm. Low blunt scales on riblets. On many shells, especially on ventral part of mature shells, scales higher and vaulted. On some shells, riblet running down crest of ribs wider and more strongly scabrous than on others. On few immature valves, low concentric lamellae conspicuous in interribs. Ventral margin moderately scalloped. Flanks (Conrad's submargins) bearing fine radial threads or radial sculpture absent. Auricles sculptured with more or less scaly riblets, those on right anterior auricle wider and more scaly than on others. Byssal notch deep, ctenolium short. Only few interiors available. Three posterior cardinal crura and one anterior on a right valve (pl. 97, fig. 4); a pair of auricular tubercles.
Length 40.8 mm, height 40 mm, convexity (both valves 13.2 mm (larger figured specimen). Length 59.5 mm, height 57 mm, convexity about 7 mm (largest specimen, a topotype). Type material: Lectotype, herewith designated, the valve illustrated by Brown and Pilsbry, Acad. Nat. Sci. Philadelphia 3894. Type locality: "Pecten bed" at tower N, (Panama Canal, west side of Las Cascadas Reach), Canal Zone, La Boca formation. Though Aequipecten canalis occurs in the Alhajuela formation, it is preeminently a species of the La Boca formation (some 190 specimens, ranging in length from 13 to 59.5 mm), especially in the Gaillard Cut area. It is especially abundant in the type region, in the collections from MacDonald's measured section mentioned under Amusium sol, including 41 topotypes. Nearly all, however, from all the localities are more or less imperfect, especially in the loss of auricles, and only eight are articulated, five of which were collected at locality 101h. Only six interiors are available.» 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. 591]
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Aequipecten canalis (Brown and Pilsbry); W. P. Woodring, 1982, Geology and paleontology of Canal Zone and adjoining parts of Panama, pl. 97, figs. 4, 7.
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