Biotic Crises and Giantism of Radiolarian Skeletons in the Late Paleozoic

Resumo

The phenomenon of giantism and minimalism in the skeleton of Late Paleozoic radiolarians is very unusually and has not yet been studied. However, this is not ugliness, but inherited morphological features, probably reflecting environmental influences and habitats. The analysis of 618 radiolarian skeletons has shown (1) inverse role of giant and small individuals in the Devonian (2% of giants and 11.7% of dwarfs) and Carboniferous–Permian (22.5% of giants and 2.2% of dwarfs); (2) a general trend toward increasing maximum conditional diameter of a conditional cell, which became 11 times greater, changing from 2% in the Devonian to 21.5% in the Carboniferous–Permian. This trend toward increasing size of skeletons and giantism in Late Paleozoic radiolarians could have indicated degeneration and reflected decline of radiolarians before mass extinction at the boundaries of the Devonian and Carboniferous (97.8% of species), Permian and Triassic (99.0% of species).