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Animal EvolutionInterrelationships of the Living Phyla$
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Claus Nielsen

Print publication date: 2011

Print ISBN-13: 9780199606023

Published to Oxford Scholarship Online: December 2013

DOI: 10.1093/acprof:oso/9780199606023.001.0001

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Phylum Bryozo (Ectoprocta)

Phylum Bryozo (Ectoprocta)

Chapter:
(p.208) 38 Phylum Bryozo (Ectoprocta)
Source:
Animal Evolution
Author(s):

Claus Nielsen

Publisher:
Oxford University Press
DOI:10.1093/acprof:oso/9780199606023.003.0038

The phylum Bryozoa (Ectoprocta) is comprised of approximately 6,000 living species of sessile, colonial, aquatic organisms and has an extensive fossil record that dates back to the Early Ordovician. There are two known classes of bryozoans, Gymnolaemata and Phylactolaemata. Extant gymnolaemates are generally classified in Eurystomata, characterised by a ‘normal’ embryology with planktotrophic or lecithotrophic larvae, and Cyclostomata (the only living order of the group Stenolaemata), which possess specialised gonozooids and exhibit polyembryony. All zooids develop by budding, making it impossible to relate their orientation to the larval organisation. All gymnolaemates display similar settling behaviour and the first phases of the metamorphosis, but the later stages vary considerably. Cyclostomes have a highly specialised type of reproduction with polyembryony. The Bryozoa has an unquestioned monophyly, although this is not supported by some earlier molecular phylogenies.

Keywords:   bryozoans, Bryozoa, Gymnolaemata, Phylactolaemata, gymnolaemates, Eurystomata, embryology, Cyclostomata, polyembryony, cyclostomes

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