Morphogenesis of Zooids of Melicerititida (Bryozoa, Stenolaemata)

An attempt was made to reconstruct the processes of zooid morphogenesis in completely extinct bryozoans of the order Melicerititida (Middle Jurassic–Paleocene). A comparative analysis of the nature of morphogenesis in these bryozoans and Tubuliporida (Stenolaemata), putative ancestors of Melicerititida, revealed a regular repetition of the initial stages of ontogeny of the ancestrula and zooids budded from it and from each other, and a fundamental difference in the last stages of zooid ontogeny in bryozoans of these two orders. The established skeletal morphology of Melicerititida zooids distinguishes them at the morphological and evolutionary levels not only from Tubuliporida, but also from all other orders of the class Stenolaemata (Cambrian–present).