Exogone Örsted, 1845

Guillermo San Martin, 2005, Exogoninae (Polychaeta: Syllidae) from Australia With the Description of a New Genus and Twenty-two New Species, Records of the Australian Museum 57, pp. 39-152 : 108

Genus Exogone Örsted, 1845

Exogone Örsted, 1845: 20 .

Diagnosis. Body small, slender, more or less filiform. Prostomium with 3 antennae, exceptionally without antennae; usually 4 eyes, sometimes also with 2 eyespots, occasionally without eyes. Palps well developed, completely fused to each other or with terminal notch. Single pair of minute tentacular cirri. Dorsal cirri usually small, papilliform to oval, present on all segments or absent on chaetiger 2 in adults of some species. Usually compound chaetae and dorsal and ventral simple chaetae; sometimes blades fused to shafts or without blades, forming simple chaetae. Two usually long anal cirri present. Body surface smooth. Pharynx with anterior margin surrounded by soft lobes, with anterior tooth. Mature females carrying eggs ventrally, developing to embryos and juveniles, lacking capillary notochaetae (natatory chaetae); mature males with long natatory chaetae; some species shown to be viviparous.

The genus was revised by San Martín (1991a), who recognized three subgenera, Parexogone Mesnil & Caullery, 1918 ; Exogone Örsted, 1845 ; and Sylline Claparède, 1864 . This diagnosis is here slightly modified.

Type species. Exogone naidina Örsted, 1845 (Hartman, 1959).

Key to the subgenera of Exogone

1 Compound chaetae with tapering, elongated, bidentate falcigers, both teeth similar, and, sometimes, some compound chaetae on each parapodium with elongate, spiniger-like blade. Probably viviparous species (only proved on a few species) ...................................................... Parexogone

—— Compound chaetae otherwise, with both elongated, spiniger-like blades and other with short falcigers, or blades missing. Females brooding eggs ventrally, developing juveniles .............................................................................. 2

2 Compound chaetae on most parapodia with short blades, with subdistal tooth smaller than distal tooth, together a single (or few) compound chaeta with long, filiform, spiniger-like blade ............................................... Exogone

—— Compound chaetae with blades minute, fused to shafts or absent ....................................... Sylline