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Article type: Cover
1998 Volume 64 Pages
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1998 Volume 64 Pages
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1998 Volume 64 Pages
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1998 Volume 64 Pages
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1998 Volume 64 Pages
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1998 Volume 64 Pages
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Article type: Index
1998 Volume 64 Pages
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1998 Volume 64 Pages
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Toshiaki Irizuki, Osamu Fujiwara, Keisuke Fuse, Fujio Masuda
Article type: Article
1998 Volume 64 Pages
1-22
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Four sediment cores were collected from Holocene deposits along drowned valleys in Zushi (Site MB 3) and Miura Cities (Sites MB 1, 2 and 5), the Miura Peninsula, Central Japan. One hundred and thirty-two ostracode species were found in 40 samples from three of these cores (Core MB 5 was not studied). Numerical analyses of ostracode fauna in the cores reveal six biotopes : BB (muddy bottom in inner brackish bay, about 2-5m in depth); SB (muddy middle bay, about 5-10m in depth); DB (muddy middle to outer bay, about 10-15m in depth); AS (rocky shore with calcareous algae and/or sandy foreshore with Zostera under the influence of open sea); SS (open sea with a sandy beach); AB (mixture of SB and AS). Vertical changes of depositional environments at the three sites are interpreted as follows : 1) ca. 9, 500 y. B. P. : Site MB 3 was inundated with tidal flats or salt marsh, but other sites were on land; 2) ca. 8, 400-9, 000 y. B. P. : Enclosed inner to shallow middle bay areas shallower than about 10m were developed at Sites MB 2 and MB 3; 3) ca. 7, 700-8, 400 y. B. P. : Enclosed middle bay areas ca. 10m deep were developed at Site MB 1 as a result of a rapid marine transgression, whereas enclosed middle to outer bay areas of 10-20m depth were present at Sites MB 2 and MB 3; 4) ca. 7, 700-6, 400 y. B. P. : As the transgression continued, open sea waters invaded Sites MB 2 and MB 3 but not Site MB 1; 5) ca. 6, 400-3, 000 y. B. P. : With a regression about 6, 400 y. B. P., water depth decreased at all sites. The depositional environment changed into sandy bay coasts at Site MB 1 and into rocky shore with calcareous algae and/or foreshore with Zostera under the influence of open sea at Sites MB 2 and MB 3. Site MB 1 has been terrestrial since about 5, 000 y. B. P. At least seven horizons of reworked deposits (T1 to T7) have been recognized in the study cores. The ostracode fauna in two of these horizons (T1 : ca. 8, 900 y. B. P. and T2 : ca. 7, 600-7, 800 y. B. P.) shows apparent mixtures of open sea and enclosed inner bay elements, but no distinctions have been made between horizons T3 to T7 and their surroundings.
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Itaru Hayami, Masahiro Matsumoto
Article type: Article
1998 Volume 64 Pages
23-35
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Current suprageneric classification systems of scallops (superfamily Pectinoidea), which were proposed by several authors mainly on the basis of adult shell morphology, are critically reviewed, and some important characters for the macrotaxonomy are evaluated. In recent years T. R. Waller has been establishing a new classification system of this superfamily in view of the fossil records, shell microstructure and some derived characters in the early dissoconch. Because the shell morphology in early byssate stage is not related to the subsequent change of life habit and resultant convergence, Waller's system may be logically regarded as more adequate than previous ones, possibly better reflecting true phylogenetic relationship. This inference was preliminarily but successfully tested by our mitochondrial DNA phylogenetic analyses of seven pectinids from Japanese waters; for example, the molecular phylogenetic tree using cytochrome oxidase subunit I surprisingly agrees well with Waller's system. Although the results of molecular phylogenetic analyses may not directly indicate Linnean hierarchial systems, they must greatly contribute to the improvement of classification and adequate evaluation of taxonomic characters.
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Michiko Yajima
Article type: Article
1998 Volume 64 Pages
36-42
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Edmund Naumann (1854-1927) was the first professor of geology at the University of Tokyo and gave the first lecture on paleontology. Dr. Bunjiro Koto took notes of Naumann's lecture in 1878 and 1879. The contents of the note will be shown and I shall discuss the similarity with Zittel's textbook of palaeontology (1877).
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Masayuki Tashiro
Article type: Article
1998 Volume 64 Pages
43-48
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Evolutionary and extinction patterns of Cretaceous bivalves in relation to taxonomic and life habit groups, and to sea-level and other environmental changes, are outlined based on the Japanese examples. Each life habit group of bivalves showed a characteristic pattern. The most distinct trend throughout the Cretaceous is the increase in the number of species of veneroids having a long siphon and pallial sinus. These veneroids shifted their habitats from brackish to marine environment. The other types of veneroids having a shorter siphon without pallial sinus, on the other hand, decreased and some of them became extinct in the Cretaceous. Among these, Pterotrigonia radiated explosively in the Cenomanian. Epifaunal bivalves, such as Ostreidae and Inoceramidae showed patterns of evolution and extinction different from those shown by infaunal bivalves.
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Masakazu Nara
Article type: Article
1998 Volume 64 Pages
49-53
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Several stratigraphic intervals characterized by crowded occurrence of Rosselia socialis, a vertical fusiform mud-lined burrow probably produced by a terebellid polychaete, are seen in the inner shelf deposits of the middle Pleistocene Ichinono Alternating beds of sand and mud, Kongochi Formation in the Boso Peninsula, Japan. Most of the specimens of R. socialis are of "stacked form" interpreted to be formed as the result of equilibrium behavior of the trace-maker. As the R. socialis-crowded beds are seen characteristically in a transgressive systems tract of a high-frequency depositional sequence, the major factor to allow dense and dominant colonization of the R. socialis animals may be explained as following. During the transgression, shoreface erosion induced frequent sedimentation in the shelf environment, and probably prohibited colonization of most benthic animals, except for the R. socialis-producers being tolerant of such a condition. The shoreface erosion also provided much organic matter, derived mainly from plants in nearshore and coastal area, to the environment, and allowed to thrive the detritus-feeding and stress-tolerant R. socialis animals.
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Yasuo Kondo
Article type: Article
1998 Volume 64 Pages
54-60
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Transgressive-regressive cycles, or depositional sequences can serve as fundamental units for taphonomic, paleoecololgical and evolutionary analyses of fossil assemblages. For benthic animals, formation of a depositional sequence means temporal changes of substrate condition, that is, erosion, condensation and rapid deposition. These are critical environmental attributes controlling colonization by benthos. Characteristics of the fossil assemblage are closely related to the stratigraphic and geographic position within the depositional sequence. This means that characteristics and patterns of change in composition of the assemblage, as well as taphonomic processes are predictable from the stratigraphic position within a depositional sequence.
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Itaru Koizumi
Article type: Article
1998 Volume 64 Pages
61-
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Yokichi Takayanagi
Article type: Article
1998 Volume 64 Pages
62-63
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Yokichi Takayanagi
Article type: Article
1998 Volume 64 Pages
64-65
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Katsumi Abe
Article type: Article
1998 Volume 64 Pages
66-67
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Toshiaki Irizuki
Article type: Article
1998 Volume 64 Pages
68-70
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Hiromichi Hirano, Hakuyu Okada, Takashi Sakai, Osamu Kinoshita, Kenich ...
Article type: Article
1998 Volume 64 Pages
71-72
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1998 Volume 64 Pages
73-86
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1998 Volume 64 Pages
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Article type: Bibliography
1998 Volume 64 Pages
87-88
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1998 Volume 64 Pages
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1998 Volume 64 Pages
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1998 Volume 64 Pages
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Article type: Cover
1998 Volume 64 Pages
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