Phylogenetic analysis of the Silurian Retiolitidae

A cladistic, phylogenetic analysis of the Retiolitidae, using 18 genera and parataxa and 23 characters, reveals that two distinct clades can be recognized within this family, as well as a primitive stem-group that includes the genus Pseudoretiolites . One of the derived clades includes Pseudo-plegmatograptus, Stomatograptus and Retiolites , which are assigned to the revised subfamily Retiolitinae. The other derived clade, the early part of which shows a paraphyletic relationship, includes the remaining known genera Rotaretiofites s.l., Paraplectograptus s.l., Sokolovograptus, Plectograptus, Agastograptus, Spinograptus, Gothograptus, Eisenackograptus, Neogothograptus, Semiplectograptus, Plectodinemagraptus and Holoretiolites . These genera are all included within an expanded Plectograptinae. The biostratigraphic distribution of these taxa suggests that these two clades diverged from a Pseudoretiolites-like ancestor in mid-Aeronian time.