Evolutionary relationships of the Early Paleozoic cyclostomatous Bryozoa

Wolinella baltica gen. et sp. n. from the Arenig of Baltic province is the oldest known single-walled bryozoan. It is characterized by cylindrical zooecia, non-pseudoporous exterior wall, and well-developed communication canals between zooecia. Wolinella is a supposed ancestor of Corynotrypa, which occurs in the lowermost Llanvirn. Evolution from the latter genus to Dentalitrypa and to the boring ctenostome Ropalonaria originated in the Caradoc. The tendency to develop a common bud in Wolinella suggests that Diploclema also may be its descendant. The genera Sagenella, Clonopora, and Kukersella, which form a morphological sequence of increasing pseudopore concentration and complexity of communication canals may have also originated from Wolinella-like encrusting forms. All post-Palaeozoic Cyclostomata could have been derived from Kukersella-like bryozoans. The morphological sequence composed by genera Wolinella, Flabellotrypa, and Ceramopora illustrates evolutionary development of colony-wide hypostegal coelom from a marginal one. Ceramopora shows a well-developed single-walled ancestrula with a large hemispherical protoecium. Hederellida are somewhat isolated among Palaeozoic bryozoans in their morphology and astogeny. They resemble Recent phylactolaemate Plumatellida both in the mode of budding, with specialized stolozooids, and shape of zooecia. Corynotrypidae fam. n., Wolinella gen. n., Wolinella baltica sp. n., W. polonica sp. n., W. brevis sp. n., Dentalitrypa infundibuliformis sp. n., Clonopora primaeva sp. n., and Kukersella erratica sp. n. are proposed.