Thalassianthidae with well developed pedal disc and rather small to medium-sized body. Column with verrucae in its upper part. Sphincter weak, restricted to circumscribed. The endocoelic tentacles (which are provided with accessory tentacles arranged in more or less distinct longitudinal rows) occupy partly the oral disc partly the oral sides of the cyclically arranged discal lobes. The aboral side of the lobes bear bunches of grape-like nematospheres. The marginal tentacles, not more than one per exocoel, are orally-aborally flattened, and their accessory tentacles are more irregularly arranged. Longitudinal muscles of tentacles and radial muscles of oral disc without tentacles. Mouth round. Several distinct siphonoglyphs not connected with directives. Numerous mesenteries, several perfect. No directives. No more mesenteries distally than proximally. Retractors well developed, diffuse, band-like. Parietobasilar muscles weak but forming a fold. Some of the perfect and the stronger imperfect mesenteries fertile. Cnidom: spirocysts, basitrichs, microbasic p-mastigophors.
T. aster Leuckart in Rueppel 1828
T. kraepelini Carlgren 1900
T. senckenbergianus Kwietniewski 1897
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1