Transactions and proceedings of the Paleontological Society of Japan. New series
Online ISSN : 2186-0963
Print ISSN : 0031-0204
ISSN-L : 0031-0204
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Volume 1978, Issue 111
Displaying 1-3 of 3 articles from this issue
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  • 691. ONTOGENETIC VARIATION OF TRIGONIOIDES (S. S.) PAUCISULCATUS (CRETACEOUS NON-MARINE BIVALVIA)
    SEONG YOUNG YANG
    1978 Volume 1978 Issue 111 Pages 333-347
    Published: September 30, 1978
    Released on J-STAGE: May 25, 2010
    DOIhttps://doi.org/10.14825/prpsj1951.1978.111_333
    JOURNAL FREE ACCESS
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    Trigonioides (s. s.) paucisulcatus shows positively the ontogenetic variation on its pseudocardinal teeth and V-shaped surface ornamentation. The number of the pseudocardinal teeth increases with growth, that is, from two on both valves (5, 3, PIII/4, 2, PII, PIV) in immature specimens, to four or five on both valves (5, 3, 1a, 1b, 1c, PIII/(6), 4, 2, 1'a, 1'b, PII, PIV) in adult specimens. The V-shaped ornamentation is gradually effaced with growth. From the comparison with T. (s. s.) kodairai from the lower stratigraphic horizon, it can be said that the phylogenetic trend is read at least on three characters ; 1) The angle of the V-ribs on the surface decreases. 2) The surface ornamentation is effaced. 3) The number of the pseudocardinal teeth increases.
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  • 692. ONTOGENIES OF FOUR UPPER CAMBRIAN TRILOBITES FROM THE BONNETERRE DOLOMITE, MISSOURI
    CHUNG-HUNG HU
    1978 Volume 1978 Issue 111 Pages 348-357
    Published: September 30, 1978
    Released on J-STAGE: May 25, 2010
    DOIhttps://doi.org/10.14825/prpsj1951.1978.111_348
    JOURNAL FREE ACCESS
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    As one of the series of papers dealing with the ontogenic changes of various Trilobita the present study clarified the ontogenic development of four Upper Cambrian species from the Bonneterre Dolomite in Missouri, i. e., Coosella prolifera, Holcacephalus tenurus, Welleraspis missouriensis and Meteoraspis globosa. Among these four species, Coosella prolifera was investigated in great detail to distinguish the metaprotaspid, paraprotaspid, early meraspid and late meraspid stages. Moreover, two different morphologic groups were clearly shown in the Coosella prolifera and Holcacephalus tenurus samples respectively throughout the ontogenic changes. These bimodal phenomena were supposed to implicate a sexual dimorphism of the trilobites.
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  • 693. ON THE GENERA SIPHONOFUSUS AND EUTHRIA OF THE INDO-WEST PACIFIC
    TSUGIO SHUTO
    1978 Volume 1978 Issue 111 Pages 358-369
    Published: September 30, 1978
    Released on J-STAGE: May 25, 2010
    DOIhttps://doi.org/10.14825/prpsj1951.1978.111_358
    JOURNAL FREE ACCESS
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    The taxonomic and stratigraphic relation of three gastropod genera Buccinulum, Euthria and Siphonofusus is reexamined. The result shows that Buccinulum and Siphonofusus derived respectively in the Early and Middle Miocene from Euthria which appeared in the Eocene. Siphonofusus, an Indo-West Pacific element, reveals a morphoseries of enlarging shell and weakening sculpture in each of its three lineages.
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