Pseudoerect Colonies and Erect Colonies with an Axial Canal and a Central Cavity in Fossil Bryozoans: Morphology and Paleoecology

The morphology of pseudoerect colonies of some fossil bryozoans of the classes Stenolaemata (orders Trepostomata and Cyclostomata) and Gymnolaemata (order Cheilostomata) is considered, that formed during overgrowth of erect substrates. Bryozoans with erect colonies with an axial canal (order Cyclostomata) and with a central cavity (order Cheilostomata) are also discussed. Using the example of the Ordovician species Hemiphragma insolitum and Orbignyella moyerokanensis (order Trepostomata), as well as of the Late Cretaceous species Meliceritites cf. acutissima and M. cf. dollfusi (order Cyclostomata), it is shown that bryozoans of the same species can have different colony morphotypes, due to their habitat conditions. Difficulties of taxonomic identification of the studied bryozoans are discussed.