Amythas Benham 1921

Genus Amythas Benham, 1921 Type species (by monotypy) and type locality

Amythas membranifera Benham, 1921. Type locality: Commonwealth Bay (Antarctica), 325 fathoms (594 m).

PROSTOMIUM. Prostomium of Ampharete -like, subdivided by a U-shaped groove; median lobe anteriorly rounded; nuchal organs and ridges absent; lower lip not enlarged and longitudinally grooved; nephridial pores/papillae not visible.

THORAX. Dorsal ridges absent.

NOTOPODIA. Modified notopodia absent.

NEUROPODIA. Neuropodia of single type, their uncini generally similar, enlarged neuropodia absent.

Jirkov (2011) proposed the inclusion of Amythas in Neosabellides Hessle, 1917 with certain doubts. However, the new material from Antarctica available for this study clarifies the position of Amythas, which is here considered valid, and its type species redescribed. The status of Neosabellides has been clarified earlier (Jirkov 2018).

Amythas has an Ampharete -like prostomium but it differs from all other known genera of Ampharetinae Malmgren, 1866 by the following combination of characters: i) absence of nephridial pores/papillae behind branchiae; ii) middle lobe of prostomium anteriorly rounded; iii) absence of nuchal ridges and any other structures of the prostomium; iv) thoracic and abdominal neuropodia of the same shape; v) absence of modified notopodia; vi) absence of dorsal ridges; vii) absence of enlarged neuropodia; viii) uncini of thoracic and abdominal neuropodia with similar morphology.

The genus Amythas also differs from Ampharete Malmgren, 1866 by the absence of a pair of nephridial papillae behind branchiae. In this aspect Amythas is close to Amage, and that is why Amythas septemdecima Schüller & Jirkov, 2013 was initially placed in Amage. Due to the above considerations, Amage septemdecima (Schüller & Jirkov, 2013) is here transferred to the genus Amythas due to the combination of characters such as the shape of prostomium, the absence of nephridial papillae behind the branchiae, the similarity of uncini and neuropodia throughout the body and the absence of any specific characters of thorax. This is in accordance to Reuscher et al. (2015), who disagreed with the fact that A. septemdecima could be settled in Amage.