Key to the families of Terebellidae sensu lato

1. Notopodia, if present, elongate, roughly cylindrical, distally bilobed; branchiae absent; ventrum of anterior segments with paired glandular pads (Fig. 2B, D) ................ Polycirridae Malmgren, 1866

– Notopodia always present, short, conical, distally bi- or single lobed; branchiae usually present; development and shape of ventral glandular areas of anterior segments variable between families, but never as paired mid-ventral pads ................................................................................................ 2

2. Thoracic uncini acicular (Figs 1A, 7D) .................................... Trichobranchidae Malmgren, 1866

– Thoracic uncini avicular (Fig. 1B–F) ............................................................................................... 3

3. Neuropodia with uncini in double rows on some segments (Fig. 6E); branchiae, if present, cirriform, arborescent or spiralled .................................................... Terebellidae Johnston, 1846 sensu stricto

– Neuropodia with uncini in single rows throughout; branchiae rarely absent, always cirriform ....... 4

4. Upper lip expanded, distinctly longer than wide (Figs 3F, 4A); neuropodia poorly developed throughout, as nearly sessile ridges and distinctly low pinnules on thoracic and abdominal segments, respectively ............................................. Telothelepodidae Nogueira, Fitzhugh & Hutchings, 2013

– Upper lip short, hood-like, about as wide as long, frequently circular (Figs 3D–E, 4B–C); welldeveloped neuropodia throughout, as fleshy ridges and elongate pinnules on thoracic and abdominal segments, respectively ............................................................................ Thelepodidae Hessle, 1917