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 : 122-124

Subgenus Exogone Örsted, 1845

Exogone Örsted, 1845: 20.

Diagnosis. Compound chaetae on all chaetigers, include both spiniger-like chaetae with fine, long, filiform, usually bifid blades and falcigers with short, bidentate blades, subdistal tooth much longer than distal tooth, shafts tips usually complex and spinose; sometimes spiniger-like chaetae of anteriormost parapodia may be absent; occasionally blades of spiniger-like chaetae modified. Tips of dorsal simple chaetae of anterior chaetigers finely spinulose subterminally and with rounded tip; dorsal simple chaetae progressively increasing in thickness posteriorly and changing slightly in shape. Antennae reduced or absent in some species.

Type species. Exogone naidina Örsted, 1845 .

Key to the species of Exogone (Exogone) recorded from Australia

1 Shafts of spiniger-like compound chaetae distally enlarged, spinose; blades of these chaetae relatively short, triangular ......................................................... 2

—— Shafts not enlarged; blades of spiniger-like compound chaetae thin, slender, filiform ...................................................................................................................... 3

2 Antennae inserted near posterior margin of prostomium; median antenna longer than combined length of prostomium and palps, spindle-shaped .................................................................................................. E. (E.) heterosetosa

—— Antennae inserted near anterior margin of prostomium; median antenna shorter than combined length of prostomium and palps together, bowling-pin shaped ........................................................................ E. (E.) heterosetoides

3 Shafts of spiniger-like compound chaetae of one of the anteriormost parapodia enlarged, provided with a triangular process ............................................................................................................................................ 4

—— Shafts of spiniger-like compound chaetae similar throughout ...................................................... 5

4 Chaetae with modified shafts on chaetiger 1 .................................................... E. (E.) longicornis

—— Chaetae with modified shafts on chaetiger 2 ............................................................. E. (E.) lourei

5 Anteriormost parapodia without spiniger-like compound chaetae ............................................... 6

—— Spiniger-like compound chaetae from chaetiger 1 ........................................................................ 8

6 Without dorsal cirri on chaetiger 2. Compound chaetae on anteriormost parapodia uniformly short with deeply bifid blades ......................... E. (E.) naidina

—— Dorsal cirri present on chaetiger 2. Blades of falcigers of anterior parapodia similar to those of remaining segments ........................................................................ 7

7 Antennae inserted on anterior margin of prostomium. Pharynx and proventricle short (through about 2 segments each). Shafts of anterior and midbody compound chaetae with long, fine spines ........ E. (E.) goorapuranga n.sp.

—— Antennae inserted on middle of prostomium. Pharynx and proventricle longer (through more than 2 segments each). Spines of shafts of compound chaetae moderately long ................................ E. (E.) arrakatarkoola n.sp.

8 Dorsal simple chaetae provided with long, fine spines (aristae) ................................................... 9

—— Dorsal simple chaetae without aristae ......................................................................................... 10

9 All antennae short. Blades of some falcigers on midbody and posterior segments strongly modified. Ventral simple chaetae without aristae ................................................................................................ E. (E.) ingridae n.sp

—— Median antenna long, similar in length to prostomium and palps together. Without strongly modified falcigerous blades. Ventral simple chaetae with aristae ..................................................................................... E. (E.) aristata

10 Median antenna distinctly longer than lateral antennae ............................................ E. (E.) dispar

—— Median antenna small, slightly longer than lateral antennae ...................................................... 11

11 Dorsal simple chaetae distinctly bidentate, with both teeth similar ................ E. (E.) haswelli n.sp.

—— Dorsal simple chaetae unidentate or indistinctly bidentate, with distal tooth reduced ...................................................................................................................... 12

12 Antennae inserted on anterior margin of prostomium. Proventricle short (through about 1–2 segments). Shafts of compound chaetae of midbody provided with a distinct, long spine ................................ E. (E.) koorenborongi n.sp.

—— Antennae inserted between eyes, on middle of prostomium. Shafts without long spines ...................................................................................................................... 13

13 Median antenna pyriform. Blades of falcigers short, encased in shafts .............................................................................................................. E. (E.) brevifalcigera

—— Median antenna ovate. Blades projecting distinctly beyond the shafts ............................................................................................................................................. 14

14 Body slender, filiform. Proventricle short (through about 2 segments) ...................................................................................................... E. (E.) breviantennata

—— Body broad. Proventricle long, through more than 2 segments ............................ E. (E.) africana