Cryptopecten yanagawaensis (Nomura & Zinbo, 1936)
NOMURA, S. & N. ZINBO. 1936. Additional Fossil Mollusca from the Yanagawa Shell-Beds in the Hukusima Basin, Northeast Honsyû, Japan. Saito Ho-on Kai Museum Research Bulletin, 10: 335-345, pI. 20. [p. 337, pl. 20, figs. 2a-b]
1936 Pecten (Aequipecten?) yanagawaensis Nomura & Zinbo, 1936
Aequipecten yanagawaensis (Nomura & Zinbo); J. Itoigawa, H. Shibata, H. Nishimoto & K. Okumura, 1981, plate 7, figures 2, 3
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«A single right (?) valve.
Shell small, suborbicular in outline, inflated, nearly as long as high, equilateral; side of disc more or less concave, apical angle about 110°, ventral margin regularly curved. Surface ornamented with subequal, rounded radial ribs which are accompanied with a thread on both sides and close to their base; interspaces rather deep, broader than ribs themselves, sculptured by fine transverse Iines. Ears imperfect, preserved one ornamented with unequal radial riblets crossed by fine growth-lines. Height 20 mm., length 21.5 mm., depth 5 mm. Pecten (Aequipecten) vesiculosus (DUNKER), a recent as well as fossil species in Japan, is somewhat allied to this new form, but the latter has smaller and more numerous radial ribs. Loc.— Yanagawa-mati, Reg. No. 8353.» SHICHIHEI NOMURA & NOBORU ZINBÔ, 1936
[Original description from J. Itoigawa, H. Shibata, H. Nishimoto & K. Okumura, 1982] |
«COMPARISON WITH FOSSIL SPECIES:— As pointed out by Vokes (1967 and 1980), Aequipecten Fisher, 1886, was proposed earlier than Cryptopecten Dall, Barsh and Rehder, 1938. On the basis of fossil material the following species have been reported under the genus Aequipecten in Japan (Masuda and Noda, 1976), vesiculosus (Yokoyama, 1911 and 1922), kyushuensis (Nagao, 1928), kikaiensis (Nomura and Zinbo, 1934), yanagawaensis (Nomura and Zinbo, 1936), sematensis (Taki and Oyama, 1954), hataii (Kanno, 1958) and matsunagiensis (Masuda, 1966). While, Hirayama (1954) described oyamaensis under the genus Cryptopecten. Among these species, kyushuensis, kikaiensis, sematensis and vesiculosus are considered to belong to Cryptopecten because they possess the characteristic hollow chambers on both sides of radial ribs. C. kyushuensis from the Waita Formation of the Ashiya Group is distinguishable from yanagawaensis by smaller and more convex shell, and distinctly elevated, round topped radial ribs of smaller number. C. vesiculosus from the Pliocene and Pleistocene formation of south Japan differs from the present species in having fewer radial ribs accompanied by a imbricated thread on each lateral side and a few number of imbricated intercalary threads in the interspaces of ribs on ventral part of disc, and also having flatter left valve. C. kikaiensis from Kikai-jima was icluded into nux by Hayami (1984) as subspecies. New species of Cryptopecten, C. spinosus, one new subspecies of C. vesiculosus, vesiculosus makiyamai and one new subspecies of C. nux, C. nux sematensis were proposed by Hayami (1984) respectively on the material from the Ryukyu Group in Kikai-jima, the Hosoya Silt of the Kakegawa Group and the Yabu Formation of the Narita Group. The present species is distinguishable from C. v. makiyamai and C. spinosus by its larger number of radial ribs than the latter taxa and from C. sematensis by difference of imbrication which appears in alternative disposition in sematensis. Fossil species of Cryptopecten has not been reported from the West Coast of North America.
COMPARISON WITH RECENT SPECIES:— Habe (1977) distinguished five living species of Cryptopecten in the Japanese waters. They are vesiculosus (Dunker), tissotii (Bernardi), nux (Reeve), owenii (Gregorio) and inaequivalvis (Sowerby). Subsequently, Hayami (1984) regarded tissoti and alli as synonyms of bullatus and he recognized four species of Cryptopecten, bullatus, nux, vesiculosus and phrygium. C. nux (Reeve) known from the Early Miocence to Recent in the Indo-Pacific is distinguishable from the present species by its smaller and more convex shell. C. bullatus (Dautzenberg and Bavay) from the Late Pliocene to Recent in the South-east Asia is also different from the present species by the smaller number of radial ribs and flatter left valve. Fossil and recent vesiculosus is distinguishable from the present species by its smaller number of radial ribs, intercalary imbricated thread between radial ribs and flatter left valve. C. phrygium (Dall) from the western Atlantic Ocean differs from the present species by its smaller number of radial ribs and poorly developed byssal notch in right valve. PHYLOGENY:— Masuda (1958a and 1962a) and Hayami (1973) considered that C. yanagawaensis is an ancestral to C. vesiculosus. Subsequently, Hayami (1984) mentioned that the phylogeny of Cryptopecten can be divided into C. vesiculosus and C. nux lines by the manner of disposition of imbricated scales and that C. vesiculosus is the direct off-shoot of the present species. However, according to the observation by the present author, Cryptopecten from the Kumano Group, Wakayama Prefecture, shows an intermidiate number of radial ribs between the present species and vesiculosus and its manner of disposition of scales is the opposite type (Chijiwa and Tomita, 1985). The specimens from the Kumano Group may represent an intermediate taxon between C. yanagawaensis and vesiculosus in that phyletic line.» SATO, Y. 1991. Paleontological study of molluscan assemblages of the Miocene Moniwa Formation, Northeast Japan and description of their Pectinidae. Report, Geological Survey of Japan, 272: 1-249, pls. 1-34. [p. 72, 75]
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Cryptopecten yanagawaensis (Nomura and Zinbo); Y. Sato, 1991, Paleontological study of molluscan assemblages of the Miocene Moniwa Formation, plate 12, figures 1-17; plate 13, figures 1-20.
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«Remarks: Numerous specimens. Cryptopecten yanagawensis was first described from the Miocene Yanagawa Formation in Fukushima Prefecture, northeast Honshu, Japan, and then it was reported from the Miocene formations such as the Moniwa Formation in Miyagi Prefecture, northeast Honshu (Masuda, 1962B), the Shukunohora and Nataki Formations of Mizunami Group in Gifu Prefecture, central Japan (Itoigawa, Shibata and Nishimoto, 1974), and the Vematsu Formation of Kumano Group in Wakayama Prefecture, central Japan (Katto and Masuda, 1979) in association with tropical or subtropical molluscs, foraminifers and others.
Cryptopecten yanagawaensis is characterized by its small inequilateral shell, about 21 elevated, more or less squarish and rounded radial ribs which are accompanied with a fine thread on both sides and interspaces between radial ribs ornamented by transverse fine lamellae. As the specimens at hand are characterized by small shell, about 22 elevated more or less squarish and rounded radial ribs which are nearly equal to their interspaces in breadth. It seems that they are conferable with Cryptopecten yanagawaensis. However, it is open to question wheter those specimens can be identified with the type specimens of yanagawaensis, because the present specimens studied are all not well preserved. To settle this problem further well preserved specimens are necessary. Occurrence: Middle Miocene upper member of Nankang Formation (Hsintien section) St 344; Middle Miocene Kuanyinshan Sandstone (Wuchi section) KS 651C, KS 654 and (Shuiliutungchi section) SLT 40M (?).» MASUDA,
K. & C. HUANG. 1990. Miocene Pelecypoda in the western foorhills of
northern Taiwan (Part II. Sistematyc description). Bulletin of National
Museum of Natural Science, 2: 141-189, pls. 1-11. [p. 146, 147]
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Cryptopecten cf. yanagawensis (Nomura & Zinbo, 1936). K. Masuda & C. Huang, 1990, Miocene Pelecypoda in the western foorhills of northern Taiwan, pl. 4, figs. 1-4.
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«Variation:— MASUDA (1958) reported that the number of radial ribs varies between 16 and 26 (averaging 21) on both valves, but it ranges from 27 to 26 (averaging 23) on both valves in the present material (Fig. 3 and 4). Its range, is nearly equal to that of Recent Cryptopecten vesiculosus. Apical angle (A.A.) is independent of shell height and ranges from 86° to 101° (averaging 92°) on the right valve and from 86° to 98° (averaging 90°) on the left valve. As a rule, there is no intercalary rib or thread on the interspaces between radial ribs, but an intercalary thread is rarely found at posterior and anterior ends. The last mentioned type is also found in the specimens collected from the Bihoku Group, Okayama Prefecture. Two phenotypes recognized in the Pliocene and Recent C. vesiculosus regarding the relative elevation of radial ribs (HABE and KOSUGE, 1967 and HAYAMI, 1973 and 1984) can not be observed in the present material of C. yanagawaensis. Shell-width increases more rapidly than shell-height after certain stage of growth as mentioned before, but there is a type with shell height still larger than shell-width even in the adult stage (fig. 15 and 16 in pl. 36. and fig. 77 a and 18 in pI. 37.). Specimens of this type are usually observed in those specimens collected from L 2. In this type, however, the other characteristics of morphology are the same as those of the normal type.
Comparison with fossil species:— As pointed out by VOKES (1967 and 1980), Aequipecten FISHER, 1886 was proposed earlier than Crytopecten DALL, BARTSCH and REHDER, 1938. On the basis of fossil material the following species have been reported under the genus Aequipecten in Japan (MASUDA and NODA, 1976); vesiculosus (YOKOYAMA, 1911 and 1922), kyushuensis (NAGAO, 1928), kikaiensis (NOMURA and ZINBO, 1934), yanagawaensis (NOMURA and ZINBO, 1936), sematensis (TAKI and OYAMA, 1954), hataii, (KANNO, 1958) and matsunagiensis (MASUDA, 1966). While HIRAYAMA (1954) described oyamaensis under the genus Cryptopecten. Among these species, kyushuensis, kikaiensis, sematensis and vesiculosus are considered to belong to Cryptopecten because they posses the characteristic hollow chambers on both sides of radial ribs. C. kyushuensis is distinguishable from yanagawaensis by smaller and more convex shell, and distinctly elevated, round topped radial ribs of smaller number. C. vesiculosus from the Pliocene and Pleistocene formations differs from the present species in having fewer radial ribs accompanied with a imbricated thread on each lateral sides of them and a few number of imbricated intercalary threads on the interspaces of ribs on lower part of disc, and also having flatter left valve. C. kikaiensis was included into nux by HAYAMI (1984) as subspecies. New species, of Cryptopecten, C. spinosus, and two new subspecies of C. vesiculosus, vesiculosus makiyamai and v. sematensis, were proposed by HAYAMI (1984). Present species is distinguishat¡ie from makiyamai, and spinosus by their larger number of radial ribs than the latter and from sematensis by difference of imbrication which appears in alternative disposition in sematensis. Fossil species of Cryptopecten has not been reported from the the West Coast of North America. Comparison with recent species:—HABE (1977) distinguished five living species of Cryptopecten in the Japanese waters. They are vesiculosus, tissotii, nux, owenii, and inaequivalvis. Subsequently, HAYAMI (1984) regarded tissoti, and alli as synonyms of bullatus and he recognized four species of Cryptopecten, bullutus, nux, vesiculosus and phrygium. C. nux (REEVE) known from the Early Miocene to Recent in the Indo-Pacific is distinguishable from the present species by its smaller and more convex shell. C. bullatus (DAUTZENBERG and BAVAY) from the Late Pliocene to Recent in the Southeast Asia is also different from the present species by the smaller number of radial ribs and flatter left valve. Fossil and Recent vesiculosus is distinguishable from the present species by its smaller number of radial ribs, intercalary imbricated thread between radial ribs and flatter left valve. C. phrygium (DALL) from the western Atiantic Ocean differs from the present species by its smaller number of radial ribs and ill-developed byssal notch in the right valve. Affinity:— MASUDA (1958 and 1962) and HAYAMY (1973) considered that C. yanagawaensis is an ancestral to C. vesiculosus. Subsequently, HAYAMI (1984) mentioned that the phylogeny of Cryptopecten can be divided into C. vesiculosus and C. nux lines by the manner of disposition of imbricated scales and C. vesiculosus is the direct off-shoot of the present species. However, according to the observation of the present author, Cryptopecten from the Kumano Group, Wakayama Prefecture, show an intermediate number of radial ribs between the present species and vesiculosus and its manner of scale disposition is the opposite type. The specimens from the Kumano Group may represent an intermediate taxon between C. yanagawaensis and vesiculosus in that phyletic line.» SATO, Y. 1984. Redescription of Cryptopecten yanagawaensis (Nomura and Zinbo) (Palaeontological study of the molluscan fauna from the Moniwa Formation part-2). Memoirs of the Faculty of Sience, Kyushu University, [Serie D - Geology], 25 (2): 247-269, text-figs. 1-7, tabs. 1, 2, pls. 36, 37. [p. 260-263]
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Cryptopecten yanagawaensis (Nomura and Zinbo); Y. Sato, 1984, Redescription of Cryptopecten yanagawaensis, plates 36, 37.
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«Remarks.— The present species was fully described by Masuda (1958) on the basis of abundant specimens from the Moniwa Formation in the environs of Sendai. The present sample Mn (Y) coincides well with them and also with the holotype from the Yanagawa Formation. Masuda (1958) understandably regarded this species as an early representative of Cryptopecten, though subsequently it was referred to Aequipecten together with some living species from Japan (Masuda,1962; Masuda and Noda, 1976). Masuda (1958, 1962) noted that the number of radial ribs varies from 16 to 26 inhis material, but my observation of the sample Mn (Y) and the pooled specimens in Tohoku University and the Saito Ho-on Kai Museum leads me to believe that the variation may not be so wide; most specimens possess 21 to24 ribs. This conclusion seems to agree well with Mr. Y. Sato's unpublished morphometric data on some samples of the same species.
Owing to the coarse-grained matrix and pre-depositional abrasion, the detailed structure of the radial ornaments is in most cases difficult to observe, and imbricated scales on the hollow parts are almost entirely lost in most specimens. However, they are clearly observable in a few well-preserved specimens. The left valve illustrated by Masuda (1958, pl.26b, fig. 8) is an exceptionally good specimen, showing the characteristic sculpture of Cryptopecten type and oppositely disposed imbricated scales. Shikama (1973) recorded the occurrence of this species from the (?) Late Miocene Zushi Formation of Miura Peninsula. Though I have inquired at the store room of the Yokohama National University where the collection related to this paper is supposed to be preserved, I could not find the relevant specimens. Aside from this occurrence, hitherto known stratigraphic occurrences of C. yanagawaensis seem to be restricted to the Middle Miocene in north and central Honshu. Several specimens from the Akeyo Formation in the Mizunami area and the Sunakozaka Formation in the Kanazawa area are undoubtedly referable to this species. Aequipecten matsunagiensis Masuda, 1966, from the (?) Middle Miocene Higashi-innai Formation in Ishikawa Prefecture (central Honshu), is probably not a representative of Cryptopecten, because the irregularly bifurcated radial ribs in the holotype (Masuda, 1966, pl. 35, fig. 4) are not to be found in this genus. I think that this species is rather closely related to Chlamys otukae Masuda and Sawada, 1960. However, one of the paratypes of A. matsunagiensis (Masuda,1966, pl. 35, fig. 6) shows regular and simple radial ribswhich remind me of those of C. yanagawaensis. The present species resernbles C. bullatus inthe large number comparatively of radial ribs on the disk weak shell convexity and low outline. In some other characteristics, especially in the considerably thick test, flat-topped central ridge of each rib and oppositely arranged imbricated scales, ir is rather similar to Phenotype Q of C. vesiculosus. In this respects, C. yanagawaensis is morphologically intermediate between the two species but clearly distinguishable from them. Distribution.— This species is known from the Yanagawa Formation at Yanagawa, Fukushima Prefecture (type locality), the Moniwa Formation at Moniwa and Jûnishin (Masuda, 1958), Taira (Masuda and Takegawa, 1965) and Kanagase and Ôgawara (IGPS no. 90785) near Sendai, Miyagi Prefecture, the Akeyo Formation, (Shukunohora Sandstone) at Mizunami and Nataki (Itoigawa, Shibata and Nishimoto, 1974), Gifu Prefecture, and the Sunakozaka Formation at Higashi-ichise near Kanazawa (Ogasawara, 1976), Ishikawa Prefecture. Early Middle Miocene (15-16 Ma).» 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. 114, 115]
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Cryptopecten yanagawaensis (Nomura and Zinbo); I. Hayami, 1984, Natural history and evolution of Cryptopecten, plate 8, figures 6-9.
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«Description:— Shell rather small in size, sub-orbicular in outline. Shell nearly equal in length and height, nearly equilateral, inflated and moderately thick. Both dorsal margins rather long and slightly concave and nearly equal in length. Ventral margin well convex. Surface sculptured with about 22, roundly elevated radial ribs and weak radial threads on both sides. Interspaces of ribs nearly equal in width and with transverse fine lamellae. Beak small, not prominent. Anterior ear larger than that of posterior, alate in outline and sculptured with 4, rather strong, round-topped radial ribs and fine concentric lines. Byssal notch deep but narrow. Posterior ear triangle in outline and sculptured with one strong and few distinct radial threads. Hinge line nearly straight but slightly bent up at beak. Resilifer pit narrow and shallow. Ctenolium well developed below byssal notch. Inner surface shallowly folded according to external sculptures.
«Remarks:— The present species allies to Aequipecten vesiculosus (Dunker), the Recent species of warm water seas, in shell outline, but the former differs from the latter in having fewer radial ribs, interspaces sculptured with a few imbricated intercarary threads on lower part of disc and narrowly spaced rib interspaces.
The present species has been known from the Miocene Yanagawa and Otsutsumi formations, Miyagi Prefecture. Locality and Formation:— River side cliff of Asano-gawa at Higashi-Ichise, Kanazawa City, Ishikawa Prefecture, Loc. No. Su-1, Sunakozaka Formation.» OGASAWARA, K. 1976. Miocene Mollusca from Ishikawa-Toyama Area, Japan. The Science Reports of the Tōhoku University [2nd. Series -Geology], 46 (2): 33-78, pls. 11-15. [p. 44, 45]
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Aequipecten yanagawaenis (Nomura and Zinbo, 1936); K. Ogasawara, 1976, Miocene Mollusca from Ishikawa-Toyama Area, Japan, plate 12, figure 3, 6.
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«Remarks: — This species resembles Aequipecten vesiculosus (Dunker), but differs in having fewer radial ribs accompanied with a rather distinct, imbricated thread on both sides of ribs and sometimes divide into two parts by very shallow longitudinal furrow near the ventral margin, by the interspaces sculptured with a few imbricated intercalary threads on about lower part of disc, and by the radial ribs which are distinctly elevated and much narrower than interspaces in the left valve.
The number of radial ribs varies from 16 to 26, but among them the most frequent number is 21. Type locality, Geological formation and Age: — Cliff of the Hirose River at the southeast end of the Yanagawa Park, Yanagawa-machi, Date-gun, Fukushima Prefecture (Lat. 37°51'05"N., Long. 140°36'05"E.). Yanagawa formation. Early Miocene. Distribution: — Yanagawa formation, Fukushima Prefecture; Moniwa member of Hatatate formation, Miyagi Prefecture; Nagaoka formation, Tochigi Prefecture; Shukunohora formation, Gifu Prefecture: all Early Miocene in age. Occurrence: — Rare in the conglomeratic coarse-grained sandstone of the Yanagawa formation; common in the granule conglomerate to conglomeratic very coarse-grained sandstone of the Moniwa member; few in the very coarse-grained sandstone of the Shukunohora formation.» MASUDA, K. 1962. Tertiary Pectinidae of Japan. Science Reports of the Tohoku University [2nd. Series - Geology], 33 (2): 117-238, pls. 18-27. [p. 192]
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Aequipecten yanagawaensis (Nomura & Zinbo); K. Masuda, 1962, Tertiary Pectinidae of Japan, plate 26, figure 8.
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«Remarks:— This species is characterized by its small inequilateral shell, about 21 elevated, more or less squarish, rounded radial ribs which are accompanied with a fine thread on both sides, interspaces which are ornamented by transverse fine lamellae, triangular posterior auricle of the right valve which is truncated behind at about right angle, conspicuous cardinal crura ornamented by fine transverse incision, and characteristic inner marginal serration. Usually the radial ribs are round-topped, but in very well preserved specimens the radial ribs are sometimes ornamented by very fine transverse lamellae. The number of radial ribs varies from 16 to 26, but among them the most frequent number is 21.
This species resembles Cryptopecten vesiculosus (DUNKER) which occurs as Recent in the Southwestern Pacific and as fossil in the Pliocene and Pleistocene of Japan, but it differs therefrom in having a less number of lamellated radial ribs which are separated into two parts by a furrow near the ventral margin in adult specimens, by the interspaces sculptured with a few imbricated radial threads at about the lower half of disc, and by the radial ribs being much narrower than the interspaces in the left valve. The geological formations from which yanagawaensis is known to occur are the Yanagawa formation in Fukushima Prefecture, and the Moniwa and Ôtsutsumi formations in Miyagi Prefecture. The rocks from where yanagawaensis has been collected or reported from consist of coarse-grained sandstone or granule conglomerate. The conditions of the sea bottom on which yanagawaensis once lived may be interpreted from the nature of the rock which preserved it. The thermal conditions of the sea at the time of building of the Yanagawa, Moniwa and Ôtsutsumi formations are judged from the associated fauna of the present species. At Moniwa, this species occurs as isolated valves in granule conglomerate or coarse-grained sandstone in which abundant pectens, other pelecypods, some gastropods. echinoids, balanids, brachiopods, bryozoan-fragments and corals occur in association. The majority of them are arranged parallel with the bedding plane and with their convex side upwards, and the majority of the observed specimens are more or less water-worn. From the mode of occurrence and the state of preservation, it is inferred that the shells of this species may have been transported from the site of living to that of burial. However, it is thought that the distance of transportation was not great and also that the present species probably preferred a shallow water bottom free from muddy materials, and influenced by warm thermal conditions. The geologicaI range of yanagawaensis is restricted to the Early Miocene in a twofold division. As noticed in early lines, the present species is closely related to Cryptopecten vesiculosus (DUNKER), and it may be the ancestral form of vesiculosus, but further materials are neccessary to settle this problem.» MASUDA, K. 1958. On the Miocene Pectinidae from the Environs of Sendai; part 10, On Pecten (Aequipecten) yanawaensis Nomura and Zinbo. Transactions and Proceedings of the Palaeontological Society of Japan [N. S.], 30: 189-192. [p. 191]
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Criptopecten yanawaensis (Nomura and Zinbo); K. Masuda, 1958, On the Miocene Pectinidae from the Environs of Sendai; part 10, On Pecten (Aequipecten) yanawaensis Nomura and Zinbo, plate 27b, figures 1-8.
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