Fig. 6: Phylogenetic position of Setapedites abundantis gen. et sp. nov. among panchelicerates, showing early euchelicerate body plan evolution.
From: Lower Ordovician synziphosurine reveals early euchelicerate diversity and evolution
Simplified extended majority rule tree of a Bayesian analysis chronogram of euchelicerate relationships, based on a matrix of 39 taxa and 114 discrete characters, showing the position of Setapedites abundantis within Offacolidae. Lineages extending after the Silurian are indicated with arrowheads. Schematic models of the body organization in Habelia, Setapedites abundantis, Dibasterium, Offacolus, and Xiphosurida illustrate the origin and early evolution of euchelicerate uniramous prosomal appendages and tagmosis. Roman numbers designate somites. Prosoma somites are highlighted in blue, pre-abdomen somites in yellow, abdomen somites in brown, and the possible anal pouch or post-ventral structure (pvs) in purple. Black dorsal lines indicate tergites and cephalotorax. Schematic model of Xiphosurida Offacolus, and Dibasterium from45, Habelia based on description from12. See Supplementary Fig. 6 for the full phylogenetic tree and Supplementary Data for phylogenetic characters and matrix.
