Adeonid bryozoans construct antler-like erect colonies and are common in bryozoan assemblages along the Japanese Pacific coast. The taxonomy of Japanese adeonid species, however, has not been studied since their original descriptions more than 100 years ago. In the present study, adeonid specimens from historical collections and material recently collected along the Japanese coast are examined. Eight adeonid species in two genera were detected, of which Adeonella jahanai sp. nov., Adeonellopsis parvirostrum sp. nov., and Adeonellopsis toyoshioae sp. nov. are described as new species based on the branch width, size and morphology of frontal or suboral avicularia, shape and size of areolar pores, and size of the spiramen. Adeonellopsis arculifera (Canu & Bassler, 1929) is a new record for Japan. Lectotypes for Adeonellopsis japonica (Ortmann, 1890) and Adeonella sparassis (Ortmann, 1890) were selected among Ortmann’s syntypes. Most species of Adeonellopsis around Japan have a southern distribution from Sagami Bay to Okinawa, while A. japonica shows a more northern distribution from Kouchi to Otsuchi. In contrast, Adeonellopsis arculifera was collected only from southwestern Japan. A key to Japanese adeonid species is provided.
Adeonella, Adeonellopsis, diversity, distribution, Japan.