Genus Thelepus Leuckart, 1849

Thelepus.— Hutchings & Glasby 1987: 226.

Type-species. Amphitrite cincinnata Fabricius, 1780, by original designation.

Diagnosis. Transverse prostomium attached to dorsal surface of upper lip; basal part usually with eyespots; distal part low, restricted to base of upper lip. Buccal tentacles all uniformly cylindrical. Peristomium forming lips, sometimes continuing dorsally as narrow annulation, with nuchal organs as a thin ciliated row on anterior margin; short, hood-like upper lip, about as long as wide; lower lip also short, button-like, restricted to oral area. Short anterior segments, usually visible all around body, segment 1 frequently with ventral lobe posterior to lower lip, lobes on following anterior segments absent. Branchiae usually present, 2–3 pairs beginning from segment 2, each pair with numerous independent curled filaments, progressively tapering to tips, mid-dorsal gap between filaments of each side either present or absent. Anterior body highly glandular ventrally, swollen, smooth to strongly tessellated. Notopodia beginning from segment 3, extending for variable number of segments; conical and relatively short notopodia, distally bilobed, chaetae emerging between lobes. Winged notochaetae in both rows, those from anterior row broadly-winged in several species, with wings slightly twisted. Neuropodia beginning from segment 5, as fleshy ridges anteriorly, as raised pinnules after termination of notopodia. Neurochaetae throughout as short-handled avicular uncini, with dorsal button at anterior third of base or terminal, prow, if conspicuous, usually distinctly short, and strongly curved, convex base in most taxa; uncini usually arranged in single, straight rows, a few species with uncini arranged in curved, C-shaped to looped rows. Nephridial and genital papillae usually present, posterior to bases of notopodia of segments 4–7. Pygidium smooth to slightly crenulate.

Remarks. Thelepus is very similar to Streblosoma, the only difference between these genera being the segment from which notopodia begin, segment 2 in Streblosoma, segment 3 in Thelepus. Like Streblosoma, this is a large genus, present worldwide, currently containing more than 40 species, of which seven are recorded from Australia. Of these seven species, one was originally described from Lizard Island, T. alatus Hutchings & Glasby, 1987, but this species was not found among the material examined for the present study.