書誌事項
- タイトル別名
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- Life orientation of heteromorph ammonites under the negatively buoyant condition : a case study on the Eubostrychoceras muramotoi Matsumoto
- イジョウカン アンモナイト ノ チャクテイジ ニ オケル セイソク シセイ ノ フクゲンホウ : Eubostrychoceras muramotoi Matsumoto オ レイ ニ シテ
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To restore the living attitude of Eubostrychoceras muramotoi Matsumoto, 1967, from the Upper Cretaceous of Hokkaido, Japan, computer simulations based on a newly developed hydrostatic model with hypothesizing negative buoyancy were carried out. The adequacy of restorations was tested by the inclination of ribs which depends tightly on the life orientation of the ammonite during growth. The results of computer simulations suggest that a rapid upside-down of the shell would take place at about one and a half whorls after the shell apex when the ammonite had a small and light phragmocone. This stage corresponds well to the changes in rib inclination observed in the actual specimens, whereas it is significantly late comparative to the previous calculation with hypothesizing neutral buoyancy. These results suggest that E. muramotoi was negatively buoyant and probably had a nektobenthic mode of life. Since the life orientation is essential information for living animals, ammonites would have used it as a "guide" for morphogenesis. The establishment of the new technique covering negatively buoyant shells enables us to make some farther computer simulations in order to understand the meanings of ammonites' shell forms.
収録刊行物
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- 化石
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化石 92 (0), 19-30, 2012
日本古生物学会
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詳細情報 詳細情報について
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- CRID
- 1390282679413850752
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- NII論文ID
- 110009517868
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- NII書誌ID
- AN00041606
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- ISSN
- 24242632
- 00229202
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- NDL書誌ID
- 024021886
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- 本文言語コード
- ja
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- データソース種別
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- JaLC
- NDL
- CiNii Articles
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- 抄録ライセンスフラグ
- 使用不可