Phylogenetic model of <em>Follicucullus</em> lineages (Albaillellaria, Radiolaria) based on high-resolution biostratigraphy of the Permian Bancheng Formation, Guangxi, South China

<p>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 <em>Follicucullus</em> with 17 species: <em>F. bipartitus, F. charveti, F.</em> sp. cf. <em>F. charveti, F. dilatatus, F. falx, F</em>. sp. cf. <em>F. falx, F. guangxiensis, F. hamatus, F. monacanthus, F</em>. sp. cf. <em>F. monacanthus, F. orthogonus, F</em>. sp. cf. <em>F. orthogonus, F. porrectus, F. scholasticus, F</em>. sp. cf. <em>F. scholasticus, F. ventricosus</em> and <em>F.</em> sp. cf. <em>F. ventricosus</em>. 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 <em>Follicucullus</em> based on their morphological affinities and stratigraphic distribution. The genus <em>Follicucullus</em> originated from <em>Pseudoalbaillella fusiformis</em>, with <em>F. monacanthus</em> as the forerunner species from which two contemporary species then radiated: <em>F. dilatatus</em> and <em>F. porrectus. Follicucullus porrectus</em> is a long-lasting species, it is abundant in our material and several <em>Follicucullus</em> lineages originated from it. In terms of evolution it is considered to be the ancestor of a number of <em>Follicucullus</em> species. </p>