Family level description.
Eunicidae are common, widespread and diverse polychaetes characterised by having complex jaws of multiple pairs of maxillae and a pair of ventral mandibles; the anterior end has paired cushion-like structures (actually dorsal lips) and beaded prostomial appendages (antennae + palps) which may be 1, 3 or 5 in total number. Some have prominent comb-like gills on mid-body chaetigers. Dorsal chaetal bundles are absent; ventral bundles have capillaries, acicular hooks, compound hooks, and combs. These are robust, muscular, active, long-lived carnivores or scavengers found in a variety of habitats.
Species level technical description.
Prostomium bilobed, slightly to deeply notched, distinctly shorter than peristomium, about as wide as peristomium, at least as deep as 1/2 of peristomium. Prostomial lobes frontally rounded, dorsally flattened, median sulcus deep. Eyes present. Maxillary formula: I = 1, + 1. II = 6, + 6. III= 6, + 0 (Mx III long; located behind left Mx II). IV = 1, + 1. Number of prostomial appendages 5 - one median antenna and a pair of lateral antennae, plus a pair of palps (in lateral-most position). Prostomial appendages dissimilar in length. Median antenna longer than lateral antennae. Palps shorter than lateral antennae. Peristomial (tentacular) cirri present, reach middle or anterior end of peristomium, digitiform, articulated. Branchiae present, pectinate, distinctly longer than notopodial cirri, not reduced in mid-body region. Maximum number of branchial filaments 8, first reached in chaetiger number 10, 0 anterior chaetigers with single branchial filaments, 2 posterior chaetigers with single branchial filaments, stems erect. Branchiae from chaetiger 7, last present chaetiger 33. Pectinate chaetae present, on anterior segments distally flat, distally flaring, pectinate chaetae on median and posterior segments distally flat, distally flaring. Compound (composite) falcigers present, Appendages of compound falcigers distally bidentate, Hoods of compound falcigers distally without mucros (rounded). Pseudocompound falcigers absent. Compound spinigers absent. Aciculae light yellow or translucent, acicular cores and sheaths indistinctly separated, rounded in cross-section, distally pointed (sharp or blunt). Subacicular hooks present, light yellow or translucent, cores and sheaths indistinctly separated, tridentate, with teeth in a crest, first present from chaetiger 31, present in all chaetigers thereafter, always single (except for replacements).