page_title: Bryozoa
section_title: Evolutionary family tree
hierarchical_section_title: Bryozoa / Taxonomy / Evolutionary family tree
caption_attribution_description: Edrioasteroid (Cystaster stellatus) with the bryozoa genus Corynotrypa from the Ordovician of northern Kentucky.Refs: Taylor, P.D. and Wilson, M.A. (1994), "Corynotrypa from the Ordovician of North America: colony growth in a primitive stenolaemate bryozoan", Journal of Paleontology, 68, pp. 241-257. Wilson, M.A. (1985), "Disturbance and ecologic succession in an Upper Ordovician cobble-dwelling hardground fauna", Science 228, pp. 575-577
context_page_description: Bryozoa are a phylum of aquatic invertebrate animals. Typically about 0.5 millimetres long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia. Most marine species live in tropical waters, but a few occur in oceanic trenches, and others are found in polar waters. One class lives only in a variety of freshwater environments, and a few members of a mostly marine class prefer brackish water. 5869 living species are known. One genus is solitary and the rest are colonial.
  The phylum was originally called "Polyzoa", but this term was superseded by "Bryozoa" in 1831. Another group of animals discovered subsequently, whose filtering mechanism looked similar, was also included in "Bryozoa" until 1869, when the two groups were noted to be very different internally. The more recently discovered group was given the name Entoprocta, while the original "Bryozoa" were called "Ectoprocta". However, "Bryozoa" has remained the more widely used term for the latter group.
  Individuals in bryozoan colonies are called zooids, since they are not fully independent animals.
context_section_description: Scientists are divided about whether the Bryozoa (Ectoprocta) are a monophyletic group (whether they include all and only a single ancestor species and all its descendants), about what are the phylum's closest relatives in the family tree of animals, and even about whether they should be regarded as members of the protostomes or deuterostomes, the two major groups that account for all moderately complex animals.
  Molecular phylogeny, which attempts to work out the evolutionary family tree of organisms by comparing their biochemistry and especially their genes, has done much to clarify the relationships between the better-known invertebrate phyla. However, the shortage of genetic data about "minor phyla" such as bryozoans and entoprocts has left their relationships to other groups unclear.
caption: An Upper Ordovician cobble with the edrioasteroid Cystaster stellatus and the thin branching cyclostome bryozoan Corynotrypa. Kope Formation, northern Kentucky.
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