Cryptopecten phrygium (Dall, 1886)
DALL, W. H. 1886. Reports on the results of dredging, under the supervision of Alexander Agassiz, in the Gulf of Mexico (1877-78) and in the Caribbean Sea (1879-80), by the U.S. Coast Survey Steamer “Blake”…. Bulletin of the Museum of Comparative Zoology at Harvard College, 12: 171-318. [p. 217 (Addenda & Corrigenda to part 1, 1889: pl. 40, fig. 1)]
1886 Pecten phrygium Dall, 1886
Pecten phrygium Dall; W. H. Dall, 1889, Reports on the results of dredging... “Blake”., plate 40, figure 1.
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«Shell of the general form of P. asper Sby., flattish, oblique, both valves similarly sculptured; left valve with about eighteen ribs with nearly equally wide interspaces; these ribs have three sharp thin keels upon them, a median and two lateral ones, which project on the distal margin of the valve, and, with the similarly projecting points of four intercalary smaller keels, fimbriate the margin in a remarkable manner; when perfect there are rounded scallops thrown from keel to keel close together, like the edges of a roll of coins, which hide all the keels except the extreme edge of the median keel of the ribs, which, without projecting much, forms a raphe, connecting the scalloped surface; the material of the scallops is very fragile, and when worn away leaves a totally different surface, which in this case shows a multitude of sharp thin scales (the bases of the scallops) zigzagging from keel to keel and imbricating the keels; the ears are moderate and subequal, there are about five distant narrow ridges on the anterior and two or three on the posterior ear of the left valve, with finer intercalary threads; the right valve has the ridges on the posterior ear scaly, and the byssal fasciole transversely concavely ridged; there are four or five free spines to the pectinium; the cardinal margin is straight and internally strongly vertically striate, as in very young specimens of Janira or Amusium. Height of largest valve, 36.5; width, 36.5; cardinal margin, 19.0 mm. Umbonal angle about 100°.
Dredged living at Station 32, in 95 fms., north of Yucatan Banks, in N. Lat. 23° 32' and W. Lon. 88° 5'; bottom temperature not noted, but probably about 60° F. Dead valves were found at Station 45, in 101 fms., bottom temperature 61°.75 F.; at a depth of 127 fms., off Havana, by Sigsbee; and off Grenada, at Station 244, in 792 fms. It is probably a dweller in about 100 fms. when living. The very remarkable sculpture of this species sufficiently distinguishes it from any other, and specimens not fully adult may be recognized at once by the fimbriated basal margin of the valves. It is related to P. Philippii Récluz and P. noronhensis Smith, differing from both in having more numerous ribs, flatter and similar valves (the two valves are differently sculptured in the others), and in details of form and sculpture of surface and ears. In one specimen, apparently quite adult, though not as large as one of the dead valves, there are on the interior of the valves, especially the left one, narrow lira) corresponding to grooves bounding the ribs externally, but which are hidden on the outside by the imbricated sculpture. These lira are very distinct, and are raised at the ends into a little white prominence like the lirae of A. alaskensis; one more instance of the interchangeability of characters in this group. The soft parts are streaked with purple in dots and dashes; there is an ocellus for each rib on the margin, except near the anal opening, where the mantle margin is without them, and is folded in such a way as irresistibly to suggest that it is the first step toward siphonation; there are here two very peculiar large crimson color marks on the mantle edge not duplicated elsewhere. The ocelli are of different sizes, some much larger than others. The remainder of the superficial anatomy calls for no special remark.» WILLIAM HEALEY DALL, 1886
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«Remarks.— Geographic variation in living Cryptopecten phrygium is evident in the studied material. A northern form living on the continental shelf from off of South Carolina to the Florida Keys and in the northern Gulf of Mexico is distinguished by a lower rib count from a southern form occurring in the southern Antilles and on the Guyana shelf (see preceding description). In addition, the northern form tends to be more convex and to have higher ribs and more erect commarginal lamellae in rib interspaces.
The extant species prefers water depths in the range of 90-200 m, with the total range of both live and dead specimens among the studied samples being 73-290 m. Lots containing specimens inferred to have been alive when collected are rare, suggesting that this species lives in low population densities and is probably not gregarious. A deep-water preference is also indicated for the Dominican Republic fossil representatives of this species. Locality TU 1352, which yielded the greatest number of specimens of Cryptopecten phrygium, is in the upper member of the Mao Formation where gravity flows have brought lenses of coarse material into deep-water clays (E. Vokes, 1989: 11, text-fig. 4). The only other fossils associated with C. phrygium are Dimya sp. (TU 1352) and Argopecten inaequalis (USGS 8733), both indicators of relatively deep water. Another interesting indication is taphonomic. On the specimen from USGS 8733, the vesicles, which are well preserved, are fi lled with finely crystalline pyrite, suggesting that slow burial facilitated diffusion of anoxic bottom water into vesicles. Pyrite-filled vesicles are also present in some specimens of Chagrepecten paracactaceus n. gen., n. sp. (TU 1292 and USGS 8735). Comparison.— The only other species that could be confused with Cryptopecten phrygium in the Dominican Republic Neogene is Chagrepecten paracactaceus n. gen., n. sp., which occupied similar deep-water depositional sites in the upper Gurabo and Mao formations. Compared to the latter species, C. phrygium has a deeper byssal notch that remains deep throughout ontogeny and vesicles on the left valve that slant ventrally as they approach the rib crest (Pl. 9, Fig. 1). In C. paracactaceus n. gen., n. sp. (Pl. 8, Fig. 13), these vesicles are transverse, approaching the rib crest at nearly a right angle. Cryptopecten bullatus, the extant species on the Pacific side of the Americas, differs from C. phrygium in being more inequilateral, having smaller auricles and a shorter hinge relative to shell length, and in lacking foliated-calcite re-entry on the shell interior as well as raised adductor scars. There is also a difference in microsculpture in early ontogeny. In very early ontogeny, C. bullatus has very fine antimarginal microsculpture between radial ribs at their origin, whereas this area in C. phrygium has only microscopic pits.
Evolution.— Cryptopecten phrygium is represented by too few fossil specimens to permit recognition of any evolutionary trends. On the basis of morphology, the southern form is possibly more primitive than the northern form in having a higher rib count that is more like that of C. bullatus of the eastern Pacific. Cryptopecten phrygium appears to be more derived than any Indo-Pacific Cryptopecten in having posterior auricles that are more pointed and therefore more removed from an Aequipecten outgroup.»
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. [p. 71]
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Cryptopecten phrygium (Dall, 1886); T. R. Waller, 2011, Neogene Paleontology of the Northern Dominican Republic, plate 9, figures 1-5.
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«Cryptopecten phrygium is a solitary representative of this genus in the Atlantic. It may be an uncommon species, judging from the scarceness of subsequently described specimens. In the National Museum of Natural History and the American Museum of Natural History, there are many small samples which agree well with the original description, but morphometrical treatment of the intrapopulational and geographic variations and allometric growth is difficult owing to the small number of individuals. Nevertheless, a highly negatively allometric growth of H to Z as well as of D to Z is strongly suggested. In short, every essential character indicates that this species is closely related to Pacific species of Cryptopecten.
It resembles C. bullatus in the weak convexity of both valves and the mode of radial sculpture characterized by the sharp central ridge and regularly alternate imbricated scales on the hollow parts. However, the maximum shell size is almost twice as large as that of C. bullatus. If specimens of similar size from the two species are compared, it is easy to see that C. phrygium has much taller shell than C. bullatus. Moreover, the average number of radial ribs is decidedly fewer in the present species. In the developed inner layer and clearly impressed muscle scars it may be rather similar to C. vesiculosus, but clearly differs from the Japanese species in the more numerous radial ribs, narrower central ridge, weaker shell convexity and alternate disposition of imbricated. scales. Distribution.— Living specimens of this species are known from a depth of about 200 meters. In addition to many stations in the Gulf of Mexico, this species has been known from the Atlantic coast (from Cape Cod to Florida), the Lesser Antilles and a station off Georgetown in Guiana. Recent.» HAYAMI, I. 1984. Natural history and evolution of Cryptopecten (A Cenozoic-Recent pectinid genus). The University Museum, The University of Tokyo, Bulletin, 24: 1-149, pls. 1-13. [p. 111]
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Cryptopecten phrygiun (Dall); I. Hayami, 1984, Natural history and evolution of Cryptopecten, plate 9, figures 6-9.
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«Fossil species of Cryptopecten are unknown in America outside the Caribbean region. The genus survives, however, in western Atlantic waters, where it is represented by Pecten phrygium (Dall, 1886, p. 217; 1889, pI. 40, fig. 1). That species ranges from Massachusetts to the Gulf of Mexico and the Lesser Antilles and has a considerable depth range-7 to 156 fathoms. Though most of the some 70 available lots clearly were dead shells, the type, dredged at a depth of 95 fathoms in the Gulf of Mexico, was alive. C. phrygium (maximum length 42 mm) is somewhat smaller than C. cactaceus and is less thin shelled, and its interrib radial threads are finer and more closely spaced.»
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. 595]
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Aequipecten phrygius Dall, 1886; B. K. Raines & G. T. Poppe, 2006, A Conchological Iconography, The Family Pectinidae, plate 251, figures 2-5.
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