Phylogenetic model of Follicucullus lineages (Albaillellaria, Radiolaria) based on high-resolution biostratigraphy of the Permian Bancheng Formation, Guangxi, South China
High-resolution sampling was performed on four Permian sections in Guangxi Province, South China (Gujingling, Sanpaoling, Guoyuan and Yutouling sections). We report abundant and well-preserved Guadalupian–Lopingian radiolarian assemblages, with 25 species belonging to three genera of the order Albaillellaria. Among them, the most abundant genus is Follicucullus with 17 species: F. bipartitus, F. charveti, F. sp. cf. F. charveti, F. dilatatus, F. falx, F. sp. cf. F. falx, F. guangxiensis, F. hamatus, F. monacanthus, F. sp. cf. F. monacanthus, F. orthogonus, F. sp. cf. F. orthogonus, F. porrectus, F. scholasticus, F. sp. cf. F. scholasticus, F. ventricosus and F. sp. cf. F. ventricosus. On the basis of composite stratigraphic ranges, this study suggests four Interval Zones in ascending order, namely F. monacanthus, F. porrectus, F. scholasticus and F. charveti Interval Zones. We provide a phylogenetic model for Follicucullus based on their morphological affinities and stratigraphic distribution. The genus Follicucullus originated from Pseudoalbaillella fusiformis, with F. monacanthus as the forerunner species from which two contemporary species then radiated: F. dilatatus and F. porrectus. Follicucullus porrectus is a long-lasting species, it is abundant in our material and several Follicucullus lineages originated from it. In terms of evolution it is considered to be the ancestor of a number of Follicucullus species.