Clades:
Pterobranchia;
Hemichordata; Ambulocraria;
Animals.
Genera: Rhabdopleura, Cephalodiscus, Atubaria; 25 species.
Habitat: in secreted tubes on the deep ocean floor.
ZoologyPterobranchia are mall worm-shaped animals; they feed by filtering plankton out of the water with the help of cilia attached to tentacles.
Their body has 3 parts: a wide, flattened anterior proboscis, a collar, and a trunk. The collar bears 1 to 9 pairs of large arms, each of which includes a row of tentacles along one side, covered in cilia and aid in filtering food from the water. The trunk includes a simple tubular gut, and is curved over so that the anus projects upwards, lying dorsal to the collar.They are mostly colonial, with several zooids living together in a cluster of tubes. In some species, the individual zooids within the colony are connected by stolons.
They are dioecious. Fertilised eggs hatch to produce a free-swimming ciliated planula-like larva. They also reproduce asexually by budding to create a new colony.
TaxonomyPterobranchia was established by Ray Lankester in 1877, containing 1 genus Rhabdopleura. Cephalodiscus was added soon. Electron microscope and phylogenetic analysis studies suggest that
Pterobranchia are related to the extinct graptolites