Fig. 16

Hypothetical scenario of evolutionary formation of the phoronid life cycle. I Life cycle of the last common phoronid ancestor, which was a benthic animal and had planktotrophic larva (lophotrochophore). II Life cycle of hypothetical ancestor, which was a sessile animal with pelagic larva and benthic creeping juvenile. III A generalized scheme of the life cycle of recent phoronids, which have pelagic larva and pelagic competent larva that is a juvenile. Abbreviations: a – adult animal; b – blastula; c – gastrula; d – planktotrophic larva; e – pelagic juvenile; e* – settled juvenile