A new taxon,capricornia(Hesionidae,Polychaeta), illustrating the LITU (‘Least‐Inclusive Taxonomic Unit’) concept

Abstract

Phylogenetic taxonomy is applied for the systematization of a newHesionidae, rather than the traditional Linnean system, with an apomorphy‐based definition of the name and without reference to rank. It is argued that biological diversity is better represented without species concepts, but that it is useful to specify when a name refers to a smallest known clade which currently 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 other taxon names are italicised with capital initial letter. TheHesionidaeis accordingly namedcapricornia, new taxon, and was found in shallow water at One Tree Island, Capricorn Group, southernmost part of the Great Barrier Reef.capricorniais small (length < 2 mm), and exhibits a number of larvalHesionidaecharacters, but is characterized by large paired ventrally situated penes on segment 9 in adult males. A cladistic parsimony analysis based on morphological characters ofcapricorniaand a selection of otherHesionidaeindicates that it belongs withinGyptiniPleijel 1998, and is the sister group ofAmphidurosHartman (1959).