Rhabdopleurida

Rhabdopleurida is one of three orders in the class Pterobranchia, which are small, worm-shaped animals, are the only surviving graptolites. Members belong to the hemichordates. Species in this order are sessile, colonial, connected with a stolon, living in clear water and secrete tubes called tubarium. They have a single gonad, the gill slits are absent and the collar has two tentaculated arms. Rhabdopleura is the best studied pterobranch in developmental biology.

Taxonomy
This small order is monotypic. It has only a single extant genus, containing four to six living species. Order Rhabdopleurida Fowler, 1892
 * Family Rhabdopleuridae Harmer, 1905
 * Genus Rhabdopleura Allman, 1869
 * Rhabdopleura annulata Norman, 1921 — Indo-Pacific region
 * Rhabdopleura compacta Hincks, 1880 — Atlantic
 * Rhabdopleura normani Allmann, 1869 — Atlantic and parts of the Pacific
 * Rhabdopleura recondita Beli, Cameron and Piraino, 2018 — Mediterranean
 * Rhabdopleura striata Schepotieff, 1909 — Pacific (Sri Lanka)

Nomen dubium:
 * Rhabdopleura grimaldi Julien, 1890
 * Rhabdopleura manubialis Jullien & Calvet, 1903

Extinct species:
 * †Rhabdopleura delmari Mortelmans 1955
 * †Rhabdopleura graysoni Chapman, Durman & Rickards, 1995
 * †Rhabdopleura hollandi Rickards, Chapman & Temple, 1984
 * †Rhabdopleura kozlowskii Kulicki, 1969
 * †Rhabdopleura obuti Durman & Sennikov, 1993
 * †Rhabdopleura sinica Chapman, Durman & Rickards, 1995
 * †Rhabdopleura vistulae Kozlowski, 1956