A new taxon, capricornia (Hesionidae, Polychaeta), illustrating the LITU ('Least-Inclusive Taxonomic Unit') concept

Phylogenetic taxonomy is applied for the systematization of a new Hesionida e, rather than the traditional Linnean system, with an apomorphy-based defi nition of the name and without reference to rank. It is argued that biologi cal diversity is better represented without species concepts, but that it i s useful to specify when a name refers to a smallest known clade which curr ently cannot be further subdivided; for this we apply the newly introduced concept LITU (Least-Inclusive Taxonomic Unit) for the new taxon. LITUs are made identifiable by being italicised with lower-case initial letter; all o ther taxon names are italicised with capital initial letter. The Hesionidae is accordingly named capricornia, new taxon, and was found in shallow wate r at One Tree Island, Capricorn Group, southernmost part of the Great Barri er Reef. capricornia is small (length < 2 mm), and exhibits a number of lar val Hesionidae characters, but is characterized by large paired ventrally s ituated penes on segment 9 in adult males. A cladistic parsimony analysis b ased on morphological characters of capricornia and a selection of other He sionidae indicates that it belongs within Gyptini Pleijel 1998, and is the sister group of Amphiduros Hartman (1959).