Halosydna Kinberg, 1856

Valencia-Soto, David, 2021, Scale-bearing beauty: Intertidal scale-worms (Polychaeta: Polynoidae) from Punta Blanca (Arequipa, Peru), Zootaxa 5032 (2), pp. 151-194 : 166

Genus Halosydna Kinberg, 1856

Type species: Halosydna patagonica Kinberg, 1856 .

Diagnosis. (from Salazar-Silva (2013)). Body thin, sub-rectangular, with 36 segments. Prostomium bilobed, without cephalic peaks; two pairs of small eyes, both pairs on posterior half of prostomium; three antennae, median antenna with ceratophore inserted frontally, with long, thick, style, subdistally expanded and tip filiform, surface not papillose; lateral antennae with ceratophores inserted terminally as prolongations of prostomium, at same level of ceratophore of median antenna, style of similar shape to median antenna. Two palps. Pharynx with nine pairs of marginal papillae and two pairs of hard jaws. Tentacular segment not visible dorsally, tentaculophores lateral to prostomium, tentacular cirri similar to antennae. Body with 18 pairs of elytra on segments 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 28, 30, 31, 33. Posteriormost three segments with dorsal cirri. Elytra imbricated; margins with or without papillae; surface with papillae and/or tubercles (sclerotized or vesicular). Elytrophores rounded. Parapodia biramous. Notopodia shorter than neuropodia. Neuropodia distally truncated, with small rounded lobe near acicula tip. Dorsal cirri subdistally expanded and distally with filiform tip; cirrophore basally expanded. Dorsal tubercle inconspicuous. Ventral cirri shorter than neuropodia, tapering to fine tip. Notochaetae shorter than neurochaetae; with rows of spines; less abundant than neurochaetae; the smaller curved, with blunt tip, remaining ones slender tapering to capillary tips. Neurochaetae with rows of spines on upper region, tips entire or bidentate. Anus dorsal, between segments 35–36. Pygidium with one pair of anal cirri.