New materials of Cisuralian (early Permian) radiolarians from western Cambodia: Paleobiogeographic implications in the Paleotethys

Radiolarians, including the new species Entactinia pailinensis Ito n. sp., were obtained from the Pailin area, western Cambodia. The radiolarians indicated an age around the Asselian–Sakmarian of the Cisuralian (early Permian). The new species is characterized by an evenly-sized-porous exosphere composed of a polygonal outer porous plate and circular inner porous plate with some radial outer spines. A previous study concluded that Entactinia Foreman rapidly expanded in the early–middle Cisuralian. Our discovery of this new species adds further occurrence data of Entactinia in the early–middle Cisuralian. In addition, another previous study highlighted the uneven distribution of Pseudotormentus De Wever and Caridroit compared with the wider distribution of Quadriremis Nazarov and Ormiston through the Permian, in particular the Guadalupian (middle Permian). Our results combined with those of previous studies indicate that the uneven distribution might extend back to the Sakmarian of the Cisuralian at least.