Rhabdopleurida

Rhabdopleurida is one of three orders in the class Pterobranchia, which are small, worm-shaped animals. Members belong to the hemichordates. Species in this order are sessile, colonial, living in clear water and secrete tubes called coenecium. Rhabdopleura is the best studied pterobranchs in developmental biology. Some claim Rhabdopleura is an extant graptolite.