北海道南西部,瀬棚層産石灰質超微化石群集について(その2) : Gephyrocapsa属のバイオメトリー

概要

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A biometrical study on coccoliths of the genus Gephyrocapsa from the Setana Formation, southwestern Hokkaido, was carried out by using SEM and TEM micrographs. The ratio between placolith-length and -breadth is uniform, and the number of shield-elements varies with the size of placolith, thus these cannot be taken as useful characters in distinguishing species of Gephyrocapsa. Three morphological groups are distinguished, though imperfectly, within forms with un-differentiated shield-elements, in terms of placolith-size, bridge-angle and relative pore width. However these three groups do not correspond to the known categories of Gephyrocapsa species. Gephyrocapsa protohuxleyi group (together with G. ericsonii-G. protohuxleyi transitional type) with differentiated shield-elements show similar range of continuous variation with the above mentioned three groups, and it cannot be morphologically separated. It is quite probable that the all forms of Gephyrocapsa from the Setana Formation are in fact specifically unseparable, even though they reveal considerable but morphological variation.
地学団体研究会の論文
1983-05-25