Kiyoko Kuwahara

Evolutionary patterns of Late Permian Albaillella (Radiolaria) as seen in bedded chert sections in the Mino Belt, Japan

Abstract The stratigraphic distribution of Late Permian Albaillella (Radiolaria) was studied in bedded chert sections from the Mino Belt, central Japan. There is a change in relative abundance up section, where the highest relative abundance changes from Albaillella triangularis in the lower part of the sections to the A. excelsa-A. lauta Lineage group (A. excelsa, A. sp. B, A. sp. A, A. flexa and A. lauta), then to A. levis and A. sp. aff. A. levis in the uppermost parts. The intervals of highest relative abundance are interpreted to represent each of their evolutionary acmes. A morphometric study was applied to the A. excelsa-A. lauta Lineage group where the length from proximal part of wing to aperture was measured. A gradual morphological change of this feature through time is seen in the A. excelsa-A. lauta Lineage group. The phylogenetic relationships of Late Permian Albaillella are constructed on the basis of this morphological change as observed in stratigraphic succession. An evolutionary lineage for A. triangularis-A. excelsa-A. sp. B-A. sp. A-A. flexa-A. lauta is presented.