Clavisyllis Knox, 1957

Cejp, Benjamin, Jimi, Naoto & Aguado, M. Teresa, 2023, Another piece for the syllid puzzle: A new species from Japan and its mitochondrial genome reveal the enigmatic Clavisyllis (Phyllodocida: Syllidae) as a member of Eusyllinae, Zootaxa 5244 (4), pp. 341-360 : 349

Genus Clavisyllis Knox, 1957

Clavisyllis Knox, 1957: 493 .

Type species: Clavisyllis alternata Knox, 1957 .

Diagnosis: (modified from Aguado & San Martín 2008; Knox 1957; San Martín & Aguado 2022; Watson 2009): Macrofaunal species, body broad, subcylindrical. Palps fused at base, ventrally directed. Nuchal organs form two prominent, long, sinuous nuchal epaulettes and one additional single, digitiform nuchal cirrus ( Clavisyllis alternata ), or curved epaulettes with knob-like tips ( Clavisyllis yongei ), or two prominent, long, sinuous nuchal epaulettes with anterior extensions ( Clavisyllis tenjini n. sp.). Prostomium with lateral projections in C. tenjini n. sp. Antennae, tentacular and dorsal cirri large, ovoid, inflated, with distinct cirrophores; ventral cirri ovoid. Dorsal cirri strongly alternating between lateral and dorsal segmental positions, to give the appearance of four longitudinal rows along the body. Parapodia uniramous with projecting upper lobe, 1–2 aciculae and compound heterogomph falcigers with blades having distinct bidentate tips and long spines. Pharynx and proventricle of similar length. Pharynx with single tooth or trepan of 12–13 teeth. Proventricle barrel-shaped. Member of Eusyllinae . Plesiomorphic mitochondrial gene order. Reproduction by epigamy (seen in C. tenjini n. sp.).

Distribution: Australia: Great Barrier Reef, North Queensland; New Zealand: New Plymouth, North Island and Banks Pensinsula, South Island; Japan: Ogasawara Islands.

Remarks: None of the previous authors were able to assign the genus to any subfamily of Syllidae ( Aguado & San Martín 2008; Knox 1957; Watson 2009). To date, Clavisyllis has been included in a single phylogenetic analysis based on morphological data ( Aguado & San Martín 2009). This study showed it sister to Lamellisyllis and both nested within Eusyllinae genera.