Abstract

Esthonioporina is a suborder of Trepostomata known mainly from the Ordovician - Usually regarded as containing fewerthan ten genera, this suborder has particular importance as it has been interpreted to be phylogenetically basal among stenolaemates (cy-clostomes excluded). Cladistic analysis of the suborder has been undertaken: 1. to infer the relationships between esthonioporine genera, 2.to assess whether the suborder is monophyletic, and 3. to determine its sister-group. The results indicate that the genera Esthoniopora, Es-thonioporella, Dianulites, Orbipora, Chondraulus, Nekhorosheviella, Revalotrypa and Ibexella can all be included within a monophyleticsuborder Esthonioporina, here raised to ordinal level as Esthonioporata. However, Orbiramus and Kanoshopora, which have ramose colo-nies with branches differentiated into endozone and exozone, although previously assigned to Esthonioporina, appear to belong elsewherein the Trepostomata. Using a small range of exemplar genera, cladistic analysis found Esthonioporina to form a monophyletic clade withCystoporata, which together constitute the sister-group of the other Trepostomata (i.e. Amplexoporina and Halloporina) + Cryptostomata.The new superorder Palaeostomata is introduced for the free-walled ‘Palaeozoic’ stenolaemates (i.e. orders Cystoporata, Esthonioporata,Trepostomata, Cryptostomata, Fenestrata and Timanodictyina).