Verifiability of genus-level classification under quantification and parsimony theories: a case study of follicucullid radiolarians

Abstract

The classical taxonomy of fossil invertebrates is based on subjective judgments of morphology, which can cause confusion, because there are no codified standards for the classification of genera. Here, we explore the validity of the genus taxonomy of 75 species and morphospecies of the Follicucullidae, a late Paleozoic family of radiolarians, using a new method, Hayashi's quantification theory II (HQT-II), a general multivariate statistical method for categorical datasets relevant to discriminant analysis. We identify a scheme of 10 genera rather than the currently accepted 3 genera (Follicucullus, Ishigaconus, and Parafollicucullus). As HQT-II cannot incorporate stratigraphic data, a phylogenetic tree of Follicucullidae was reconstructed for 38 species using maximum parsimony. Six lineages emerged, roughly in concordance with the results of HQT-II. Combined with parsimony ancestral state reconstruction, the ancestral group of this family is Haplodiacanthus. Five other groups were discriminated, the Parafollicucullus, Curvalbaillella, Pseudoalbaillella, Longtanella, and Follicucullus–Cariver lineages. The morphological evolution of these lineages comprises a minimum essential list of eight states of four traits. HQT-II is a novel discriminant analytical multivariate method that may be of value in other taxonomic problems of paleobiology.

New Permian radiolarians from east Asia and the quantitative reconstruction of their evolutionary and ecological significances

“…Global distribution maps for the selected radiolarian genera include all other regions in the world. Following the current concepts of radiolarian genera, Longtanella , Pseudoalbaillella sensu stricto and the Follicucullus -group ( Follicucullus and Cariver ) 12 were re-identified from illustrated specimens in publications that are archived in Tohoku University (ca. 5800 papers).…”

“…Further, it not only confirmed the validity of Longtanella but also suggested that Longtanella is an important sister group in the evolution between the genera Pseudoalbaillella sensu stricto and Follicucullus . Just before this paper 12 was accepted, the validity of Longtanella was newly morphologically confirmed 11 .…”

“…Soon after this consensus was published, this three-genera scheme was undermined by data from the North America midcontinent 5 , China 11 and Japan 3 . Xiao et al 12 re-evaluated the generic taxonomy of Follicucullidae and discussed their phylogenetic relationships using mathematical methods, such as Hayashi’s quantification theory II and parsimony theories. This study favoured these recent criticisms over the views of the PGW Group, and concluded on a ten-genera scheme, including the genus Longtanella 12 .…”

“…Xiao et al 12 re-evaluated the generic taxonomy of Follicucullidae and discussed their phylogenetic relationships using mathematical methods, such as Hayashi’s quantification theory II and parsimony theories. This study favoured these recent criticisms over the views of the PGW Group, and concluded on a ten-genera scheme, including the genus Longtanella 12 . Further, it not only confirmed the validity of Longtanella but also suggested that Longtanella is an important sister group in the evolution between the genera Pseudoalbaillella sensu stricto and Follicucullus .…”

“…In order to fulfil these objectives, we reviewed all papers with illustrations of representatives of the Follicucullidae and examined their identifications with care. In exploring the recent suggestion 12 that Longtanella could be a phylogenetic bridging genus between Pseudoalbaillella sensu stricto and the Follicucullus group (including all the species of Follicucullus and Cariver ), we reexamined all the Longtanella morphotypes from South China. Then, we explored the palaeobioprovincial scheme of these three radiolarian genera together with fusulinacean genera by using correspondence analysis (CA).…”