What is "pterobranchia"

Pterobranchia \Pter`o*bran"chi*a\, n. pl. [NL., fr. Gr. ? a wing + ? ?.] (Zo["o]l.) An order of marine Bryozoa, having a bilobed lophophore and an axial cord. The genus Rhabdopleura is the type. Called also {Podostomata}. See Rhabdopleura.

Bryozoa \Bry`o*zo"a\, n. pl. [NL., fr. Gr. ? moss + ? animal.] (Zo["o]l.) A class of Molluscoidea, including minute animals which by budding form compound colonies; -- called also Polyzoa.

Note: They are often coralike in form and appearance, each small cell containing an individual zooid. Other species grow in delicate, flexible, branched forms, resembling moss, whence the name. Some are found in fresh water, but most are marine. The three principal divisions are Ectoprocta, Entoprocta, and Pterobranchia. See Cyclostoma, Chilostoma, and Phylactolema.

Pterobranchia is a clade of small worm-shaped animals. They belong to the Hemichordata, and live in secreted tubes on the ocean floor. Pterobranchia feed by filtering plankton out of the water with the help of cilia attached to tentacles. There are about 30 known living species in the group.

The class Pterobranchia was established by Ray Lankester in 1877. It contained, at that time, the single genus Rhabdopleura. Rhabdopleura was at first regarded as an aberrant polyzoon, but when the Challenger report on Cephalodiscus was published in 1887, it became clear that Cephalodiscus, the second genus now included in the order, had affinities in the direction of the Enteropneusta.

Studies under an electron microscope have suggested that pterobranchs belong to the same clade as the extinct graptolites, and phylogenetic analysis suggests that the pterobranchs are living members of the graptolite clade.