Somalipecten cranmerorum Waller, 1986
WALLER, T. R. 1986. A new genus and species of scallop (Bivalvia: Pectinidae) from off Somalia, and the definition of a new tribe Decatopectinini. The Nautilus 100 (2): 39-46, figs. 1-13. [p. 42, figs. 1-13]
1986 Somalipecten cranmerorum Waller, 1986
T. R. Waller, 1986, figures 1-9.
T. R. Waller, 1986, figures 10-13.
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«Diagnosis: Somalipecten having four major plicae on right valve and three on left, the left valve also having a single plica of smaller amplitude adjacent to each disk flank; enlarged distally concave or enclosed scales few in number and widely spaced, limited to tops of plicae of left valve.
Description: Disk Outline ─ Moderately large, with height commonly 40 to 70 mm and seldom exceeding length, the ratio of height to length commonly 0.88 to 1.01; outline acline or slightly prosocline, rarely slightly opisthocline, and equilateral; anterior and posterior extremities of disk narrowly rounded, ventral margin broadly rounded; umbonal angle ranging from 98 to 104º; both valves convex, the right more so than the left, the umbone of left valve flattened; ratio of convexity of closed valves to height 0.22 to 0.37, averaging 0.31. Auricle Outlines ─ Right anterior auricle with byssal notch only moderately deep, bordered on its ventral side by an active ctenolium of from 3 to 5 delicate, closely spaced teeth, which may be obsolescent in largest specimens; other auricles pointed, their free margins forming acute angles with hinge line; anterior auricles exceeding posterior in length, the ratio of length of anterior outer ligament to length of posterior outer ligament commonly 1.04 to 1.24; ventral migration of ligament system absent even in largest individuals. Exterior Shell Surface ─ Right disk with 4 major plicae, at least the central ones beginning at a shell height of between 2 and 3 mm as pairs of low rounded costae with narrow raised crests, each pair then merging into a single broad rounded plica at shell height of 10 to 15 mm, the broad plica becoming flattened and bifid with the introduction of a median groove at a shell height of about 35 to 40 mm; anteriormost major plica bordered anteriorly in early ontogeny by a single costa along edge of disk flank; posteriormost major plica bordered posteriorly by a pair of costae in early ontogeny. Left disk with three major plicae bordered on anterior and posterior by a single lower plica, the broad interspaces broken by introduction of smaller median plicae corresponding to the median grooves on right plicae. Secondary radial costae beginning on tops of right plicae at shell heights between 4 and 12 mm and across both plicae and interspaces of both valves by a height of 40 to 55 mm. Disk flanks without radial or antimarginal costae. Right anterior auricle commonly with 5 to 7 costae at margin; other auricles with highly variable costation, the right posterior auricle commonly lacking or having only a few costae. Enlarged, distally concave scales, sometimes closed to form hollow knobs, limited to tops of the five major plicae of left valve, few in number and widely spaced, commonly fewer than 5 per plica, rarely absent or as many as 8 per plica. One or two commarginal ledges commonly present in distal fourth of disk. Prismatic stage of right valve extending to shell height of 1.8 to 2.3 mm. Microsculpture on left beak and early postprismatic stage of right valve before start of commarginal lamellae consisting of exceedingly fine antimarginal striae. Commarginal lamellae closely spaced throughout ontogeny, first appearing in interspaces of right disk at shell heights between 4 and 6 mm. Internal Features ─ Dentition with dorsal teeth dominant, intermediate teeth very weak or absent, resilial teeth absent. Single crus present on inner surface of shell beneath each disk flank, a second crus sometimes present on ventral fourth of posterior auricles; other crura or marginal denticles generally absent on inner surfaces of auricles. Inner surfaces of plicae with carinate edges and commonly with numerous radially elongate marginal denticles. Ostracum inside pallial line consisting entirely of lathic calcite with coarse irregular patches of folia; crossed lamellar aragonite absent in mature shells. Color ─ Basal pigment red, orange-red, or orange, either solid or broken by exceedingly fine white mottling and/or by bold oblique bars or chevrons of white; dark pigment commonly present on ventral sides of enlarged scales. Pigment more subdued on right valve than on left, the bold patterns generally restricted to left valve. Beaks commonly with fine intersecting diagonal white lines. Interior of shell commonly pigmented outside pallial line and more rarely inside pallial line by the same color present on exterior. Comparison: Somalipecten cranmerorum, new species, differs from all of the fossil species mentioned in the above discussion of Somalipecten, new genus, in having fewer major plicae. The smallest number of plicae among the fossil taxa occurs in Somalipecten wyllei (Cox, 1929), which has an additional pair of plicae on each valve, stronger intermediate hinge teeth, and no enlarged scales on the left valve. S. cranmerorum superficially resembles the more coarsely plicate varieties of Flexopecten glaber (Linnaeus, 1758) living in the Mediterranean, but that species lacks nodes and enlarged scales and differs in hinge details, as discussed above in the comparison of genera. None of the extant or extinct species of Nodipecten have as closely spaced commarginal lamellae, and they have much more massively developed dorsal and intermediate hinge teeth. Ecology: The habitat of the new species is known only from the data provided by Taiwanese fishermen, who said that the shells were trawled off Somalia at depths of 150 to 300 m. Because they have not divulged the exact locality, it is not known whether the specimens are from the Gulf of Aden or the Indian Ocean side of Somalia. Mr. T. C. Lan of Taipei, Taiwan, who obtained the specimens from the Taiwanese fishermen, has provided a list of associated species, some of which would appear to shed light on the locality of the pectinids. Strombus oldi Emerson, 1965, was originally described from the Indian Ocean side of Somalia in the vicinity of Obbia and Mogadiscio (Emerson, 1965)) and recently it also has been found off Oman in the Arabian Sea (David Hargreave, pers. com., 1986). It is not known to occur in the Red Sea or the Gulf of Aden. Cypraea broderipi Sowerby, 1832, Cypraea marginalis Dillwyn, 1817, and Vasum truncatum (Sowerby, 1892) are known mainly from the Indian Ocean and not the Red Sea (Abbott and Dance, 1982), and Mimachlamys townsendi (G. B. Sowerby 111, 1895) is known mainly from the Arabian Sea off Pakistan and from the Gulf of Oman. Although these data suggest that S. cranmerorum is from the Indian Ocean side of Somalia, the fossil species that is morphologically the closest, S. wyllei (Cox, 1929), is from a raised beach on the Red Sea coast in Sudan. The epifauna of the shells of S. cranmerorum gives some clues to living habits. The lower (right) valves of many of the uncleaned specimens are encrusted by cheilstome bryozoans at least in the dorsal region and in some cases extensively over the valve. This indicates that the lower valve was not buried in fine sediment and that the scallop must have lived attached by a byssus above the bottom or on a hardground bottom. The presence of calcareous algae on the upper valve suggests that the specimens lived in the photic zone, as does also their association with algal grazers such as Strornbus. Thirteen of the 52 specimens of S. cranmerorum examined have circular corroded patches within which a borehole occurs over the anterodorsal disk flank over the approximate position of the scallop's mouth. These features are identical to the scars produced by the calyptreacean gastropod Capulus danieli (Crosse, 1858) described by Orr (1962; see also Matsukuma, 1978) from another Indo-Pacific member of the Decatopectinini, Bractechlamys vexillum (Reeve, 1853). On the basis of gut contents, absence of damage to soft parts other than the mantle through which the boring passes, and evidence of repair and continued survival, Orr concluded that the snail-scallop relationship is one of antagonistic symbiosis, not true parasitism, the snail stealing food, probably in mucus strings, from the mouth region of the scallop. On all but one of the scarred and bored scallops, the shell damage is on the left umbo. The fact that gastropod was able to survive on the lower valve is additional evidence that the scallop lives attached above the sediment surface. Etymology: This species is named in honor of Roberta D. Cranmer and her late husband, Charles E. Cranmer, of Louisville, Kentucky, whose personal involvement and quiet philanthropy have greatly benefited many people and organizations, a number of which have made significant contributions to malacology. Holotype: USNM 859034, a pair of matching valves, height 50.0 mm, length 53.8 mm, convexity across closed valves, 15.5 mm, collected by Taiwanese fishermen off Somalia at a depth between 150 and 300 m. Material: In addition to the holotype, USNM 859034, 51 paratypes were studied, all paired valves from the same locality at 150-300 meter off Somalia. Twelve of these paratypes are deposited in the U.S. National Museum of Natural History under the catalogue numbers 859035 (the paratype illustrated herein) and 859036 (eleven unillustrated paratypes). Thirtyone of the remaining paratypes were returned to Mr. Donald Dan, and one paratype was sent to each of the following eight museums: American Museum of Natural History, New York; Natural History Museum of Los Angeles County, Los Angeles; British Museum (Natural History), London; Museum National d'Histoire Naturelle, Paris; Rijks-museum van Naturlijke Historie, Leiden; Australian Museum, Sydney; Western Australian Museum, Perth; and National Science Museum, Tokyo.» THOMAS RICHARD WALLER, 1986
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«Remarks: Hertlein (1969: N366) treated Mirapecten as a subgenus of Semipallium [Jousseaume] Lamy, 1928, which he referred to the same suprageneric group as Decatopecten. Waller (1986: 40), followed by Vaught (1989: 119), considered Mirapecten as a full genus in the tribe Decatopectinini. Somalipecten was originally differentiated from Mirapecten by the presence in the latter taxon of a deep byssal notch throughout ontogeny and of well-developed scales on its radial plicae (or at least on the posterior plica of both valves). However even within different species of Mirapecten these characters vary, so that the byssal notch may be deep or only moderately deep, and scales range from well developed to absent.»
DIJKSTRA, H. H. & R. N. KILBURN. 2001. The family Pectinidae in South Africa and Mozambique (Mollusca: Bivalvia: Pectinoidea). African Invertebrates, 42: 263-321. [p. 283]
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Mirapecten cranmerorum (Waller, 1986); B. K. Raines & G. T. Poppe, 2006, A Conchological Iconography, The Family Pectinidae, plate 76, figures 1-4.
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«Taxonomic content: The new genus [Somalipecten] includes a number of fossil species from the western Indian Ocean region described in publications by Cox (1929) and Eames and Cox (1956): Chlamys (Aequipecten) farsanensis Cox, 1929, C. (A.) isthmica (Fuchs, 1878), C. (A.) leesi Cox, 1929, C. (A,) lessepsi (Fuchs, 1878), C. (A.) pseudola Eames and Cox, 1956, C. (A.) werthi (Philippi, 1901), and C. (A.) wyllei Cox, 1929.
Stratigraphic Range: Upper Miocene to present. All of the fossil species listed above, with the exception of S. pseudola, are from deposits adjacent to the Red Sea (Egypt, Sudan, Saudi Arabia), the western Indian Ocean (Somalia, Kenya, Tanzania, Zanzibar), and the Arabian Sea (southeastern Saudi Arabia, Iran). Their age was called "post-Miocene" by Cox (1929), and some are probably as young as late Pleistocene or Holocene. S. pseudola from Iran was said by Eames and Cox (1956) to range from Upper Miocene to Pliocene. Somalipecten cranmerorum, new species, is the only known living species.» WALLER, T. R. 1986. A new genus and species of scallop (Bivalvia: Pectinidae) from off Somalia, and the definition of a new tribe Decatopectinini. The Nautilus 100 (2): 39-46, figs. 1-13. [p. 41]
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Chlamys (Aequipecten) pseuduloa sp. nov.; F. E. Eames & L. R. Cox, 1956, Some Tertiary Pectinacea from East Africa, Persia, and the Mediterranean region, plate 6, figures 1-3.
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