The Phylomorphogeneses of the Tertiary Foraminiferal Families, Lepidocyclinidae and Miogypsinidae

• Main Author: Hanzawa Shoshiro
• Format: Report
• Language: English
• Published: Tohoku University 1964
• Subjects: Planktonic foraminifera
• Online Access: http://hdl.handle.net/10097/28776; https://tohoku.repo.nii.ac.jp/?action=repository_uri&item_id=11973; https://tohoku.repo.nii.ac.jp/?action=repository_action_common_download&item_id=11973&item_no=1&attribute_id=18&file_no=1

In the younger Tertiary of the Tethyan and Caribbean-Gulf of the Mexico regions, the succession of three zones, 1) Miogypsina, 2) Nephrolepidina and 3) Eulepidina [and Lepidocyclina (s.s.) in America] and Spiroclypeus in descending order has been well established. The writer has referred these three zones to 1) Helvetian, 2) Burdigalian and 3) Aquitanian respectively and left the last stage in the Oligocene following the scheme of H. Douville and others. In the light of the recent studies of planktonic Foraminifera from Japan and Micronesia, these three zones are confirmed to belong to 1) the Globorotalia fohsi Zone, 2) Globigerinatella insueta Zone and 3) Catapsydrax stainforthi-C. dissimilis Zones respectively. The above correlation is discrepant with the scheme of the workers on planktonic Foraminifera, in which the above No. 2 zone is included in the Aquitanian stage and the last-cited stage also includes No. 3 zone. Moreover, the Oligo-Miocene boundary is drawn at the bottom of the Aquitanian. If the boundary in question is in such a manner, it falls within the range zones of significant larger foraminiferal genera, such as Eulepidina (Rupelian-Aquitanian), Lepidocyclina (s.s.) (upper Middle Eocene-Aquitanian in America) and Spiroclypeus (upper Eocene-Aquitanian). If it is drawn at the top of the Aquitanian, it falls at the datum surface, which defines the extinctions of the three distinctive genera just cited. Nephrolepidina, Pliolepidina and Triplalepidina are reinstated, although they were suppressed by Cole as to be synonymous with Eulepidina and Lepidocyclina (s.s.) respectively. And Helicolepidina and Polylepidina are excluded from the Lepidocyclinidae, but included in the Helicolepidinidae. Lepidocyclina (s.s.) which may have been derived from a stock of the Planorbulinidae independent from that of the Orbitoididae of the Maestrichtian during upper Middle Eocene is believed to have given birth to Nephrolepidina and Pliolepidina in upper Eocene, Nephrolepidina in turn to Eulepidina in the Rupelian, ...