Amussiopecten preglyptus (Olsson, 1922)
OLSSON, A. A. 1922. The Miocene of Nothern Costa Rica with notes on its general stratigraphic relations. Bulletins of American Paleontology, 9 (39): 1-460, pls. 1-32. [p. 202, pl. 17, figs. 2, 7]
1922 Pecten (Aequipecten) preglyptus Olsson, 1922
A. A. Olsson, 1922, plate 17.
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«Shell of moderate size, subcircular in form and convex; ears of usual size, subequal and with a straight hinge-line; sculpture of about 16 or 17 wide, little elevated ribs and narrower, scarcely distinguishable interspaces; the surface is otherwise smooth or with fine, concentric lines; interior of the shell with 29 or 30 Amusium-like internal lirae which are evenly spaced and not in pairs; these lirae are very faint in the middle of the shell cavity but strong distally.
Length 50, height 49, semi-diameter 6.5 mm. An Amusium-like species found in the lower sandstones and conglomerates of the Gatun formation in upper Codes Creek. It is closely related to the recent deep-water Pecten glyptus Verrill from the cost of Hatteras and Marthas Vineyard (see Dall Proc. U. S. Nat. Mus., vol. 12, p. 248, pl. 8, figs. 2, 3), both species having about the same number of low, wide ribs and internal lirae. The fossil shell seem to have been nearly circular while glyptus is decidely oblique in outline. Gatun Stage: Upper Codes Creek.» AXEL ADOLPH OLSSON, 1922
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«Although Chagrepecten paracactaceus n. gen., n. sp. in the middle Pliocene part of the Mao Formation is the geologically youngest defi nite member of the new genus, there is an extant species that might have branched off early from Chagrepecten n. gen. It is Pecten glyptus Verrill, 1882, which lives in the western North Atlantic from southeast of Cape Cod to the Florida Strait and in the northern Gulf of Mexico at depths from ca. 150-250 m. It resembles species of Chagrepecten n. gen. in shell outline, convexity, byssal notch, and ctenolium, as well as shell thickness and the distribution of foliated-calcite on inner shell layers. Although it also has broad, narrow-crested ribs comparable in profi le and number to the fossil species of Panama and the Dominican Republic, it lacks radial costellae (except in early ontogeny), a vesiculate secondary surface, and prominent commarginal lirae. There is only a vestigial trace of the latter in the form of rows of tiny cuspate lamellae in late ontogeny. Unlike the fossil species, P. glyptus has prominent disk gapes.
Pecten (Aequipecten) preglyptus Olsson, 1922, from Olsson's "Gatun Formation" in Limon Province, Costa Rica, is possibly ancestral to the extant species. Olsson's species, however, is known only from the holotype (PRI 21140), a damaged and badly worn left valve (Olsson, 1922: pl. 17, figs 2, 7). Dall also noticed the resemblance between P. cactaceus and the extant P. glyptus. In his faunal list published by Spencer (1897: 24) preceding his formal description of P. cactaceus, Dall listed the fossil species as "Pecten (like glyptus, Verr.)."» 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. 67]
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«Remarks:— As this species was based upon a poorly preserved left valve, its detailed morphological features remained unknown. It is characterized by its rather small shell, slightly inflated left valve, about 16 rounded, very low radial ribs which tend to become obsolete towards ventral and lateral margins and narrower than their interspaces in younger stage but tend to become nearly equal to their interspaces in breadth with growth; fine, regularly spaced incremental lines; distinct auricular crura terminating distally in an oblong denticle at each extremity ; distinct paired internal ribs near ventral margin; and simple cardinal crura.
This species was described under the subgenus Aequipecten but from the above mentioned morphological characteristics it is evident that it can not be referred to that subgenus but to Amussiopecten. Unfortunately the characteristics of the right valve remain unknown.» MASUDA, K. 1971. Amussiopecten from North America and Nothern South America. Transactions and Proceedings of the Palaeontological Society of Japan [N. S.], 84: 205-224, pls. 25-26. [p. 212]
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