Micronephthys Friedrich, 1939

Dixon-Bridges, Kylie, Gladstone, William & Hutchings, Pat, 2014, One new species of Micronephthys Friedrich, 1939 and one new species of Nephtys Cuvier, 1817 (Polychaeta: Phyllodocida: Nephtyidae) from eastern Australia with notes on Aglaophamus australiensis (Fauchald, 1965) and a key to all Australian species, Zootaxa 3872 (5), pp. 513-540 : 516

Micronephthys Friedrich, 1939

Micronephthys .— Hartman, 1950: 130.— Fauchald, 1977: 96 –97.— Paxton, 1974: 204.— Rainer and Kaly, 1988: 696.— Ravara et al., 2010b: 23 –24.

Type species. Micronephthys minuta (Théele, 1879) , by monotypy.

Diagnosis. Body of small size. Branchiae absent or present, if present, reduced, nearly straight and present on few chaetigers only; pre- and postchaetal lobes rudimentary ( Hartman 1950). Acicular lobes conical, neuropodial postacicular lobes absent. First chaetiger not reduced, similar to remaining ones. Barred chaetae may be present; if so, restricted to anterior chaetigers. Lyrate chaetae may be present or absent. Aciculae of median and posterior parapodia with curved tips. Antennae and palps present. Pharynx with subterminal papillae, middorsal papilla present or absent, proximal region smooth or with verrucae. Nuchal organs rounded.

Comments. This genus is now not easily distinguished from small specimens of Nephtys as they share many characters, but from the recent literature it appears the only distinguishing features are its small body size together with poorly developed parapodial lobes. Mature adults are required for correct identification to genus level. One character typically used to define the genus - "branchiae absent or poorly developed" requires some clarification by defining exactly what "poorly developed" means, as some species possess branchiae that occupy almost 1/2 to 2/3rds of the interramal space, a feature which some species of Nephtys possess also. The estimation of the size of the branchiae is also relative to the size of the interramal space, which can range from a wide V-shape, to a narrow Ushape. We have expanded the definition to include the presence or absence of verrucae on the proximal region of the pharynx as occur in several species (see Table 4 ). Ravara et al. (2010a) found that the genus Micronephthys was well supported and sister taxon to the genus Nephtys , however they suggest that it is heterogeneous and in need of revision. We agree, but this is beyond the scope of this study.