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Phylum Bryozoa

  • Subphylum Entoprocta — Middle Cambrian?, Late Jurassic-Recent

  • Subphylum Ectoprocta

    • Class Phylactolaemata — Middle Jurassic-Recent

    • Class Gymnolaemata — Early Ordovician-Recent (dominates Mesozoic-Recent)

      • Order Ctenostomida — Early Ordovician-Recent

      • Order Cheilostomida — Late Jurassic-Recent

    • Class Stenolaemata — Early Ordovician-Recent (dominates Ordovician-Permian)

      • Order Cyclostomida — Early Ordovician-Recent

      • Order Cystoporida — Early Ordovician-Late Triassic

      • Order Trepostomida — Early Ordovician-Late Triassic

      • Order Cryptostomida — Early Ordovician-Late Triassic

Bryozoans are sessile, filter-feeding organisms with a wide salinity tolerance — most are marine, but a few species (from the Entoprocta, Phylactolaemata, and Ctenostomida) inhabit fresh water and a few others (from the Cheilostomida) are found in brackish-water environments.

Bryozoans have wide latitudinal (tropical to polar), temperature, and depth ranges (0 to 8.5 km). They can be the main constituents in Mesozoic and Cenozoic temperate- and cold-water shelf carbonates, as well as in deeper shelf and slope settings; in the Paleozoic, they were more conspicuous in tropical to subtropical habitats.

Many bryozoans require a firm substrate on which to encrust; some are free living, and others have roots extending into sandy substrates. Massive and encrusting varieties are found in high-energy environments; delicate, erect varieties are indicative of low-energy environments.

Entoproct bryozoans are soft bodied and, therefore, are rarely preserved.

Most ectoproct bryozoan zooecial walls are composed of calcite (usually low-Mg calcite; a few consist of high-Mg calcite and others are partially aragonitic). Some species have chitinous or gelatinous walls.

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