Neotenotrocha sterreri gen. et sp. n. is described from Bermuda. It is a gonochoristic. interstitial polychaete exhibiting sexual dimorphism. The maximum length of males is only 140 μm. while females may be up to 255 μm long. They are thus the smallest polychaetes known to contain a mature ovary. The new species is referred to the polychaete family Dorvilleidae, primarily due to the presence of a ctenognath jaw apparatus. In almost all external characters the new form is strongly reduced. lacking parapodia, setae, antennae, and palps, whereas larval characters such as trochae and a neurotroch are retained in adults. In the light of earlier literature on phylogeny within Dorvilleidae and the likelihood that Iphitimidae and Dinophilidae are closely affiliated with the latter family, the unique combination of characters in
Neotenotrocha is of special interest. A phylogenetic analysis of all apparently valid genera in the three families leads to the hypothesis that Dinophilidae and Iphitimidae represent monophyletic and paraphyletic subgroups, respectively, within Dorvilleidae. Accordingly, the definition of Dorvilleidae is emended and a key to the genera provided. The species
Ougia macilenta (Oug, 1978) is referred to
Parougia Wolf. 1986 and the generic status of
Meiodorvillea apalpata Jumars. 1974 and
Protodorvillea gaspeensis Pettibone. 1961 is discussed. Some remarks on the applicability of concepts such as neoteny and progenesis in the characterisation of interstitial dorvilleids are included. On the basis of the cladogram and these considerations, it is hypothesized that this group may have originated in the single evolutionary event.
