Genus Siphonognathus

Previously placed in what was thought to be a temperate Australian and New Zealand fish family Odacidae, this is a diverse genus with six species having a remarkable variety of body forms. All are confined in distribution to southern and western Australia.

Key to species of Siphonognathus.
1a. Pelvic fins absent; segmented dorsal fin rays 19-22; body extremely elongate, greatest depth 17.2-27.0 in SL..........................................................................Siphonognathus argyrophanes.
1b. Pelvic fins present; segmented dorsal fin rays 11-16; body of moderate depth to elongate greatest depth 5.9-12.8 in SL…………………………………………………......................2.

2a. Segmented dorsal fin rays 14-16; total dorsal fin rays 34-36; anal fin rays 7-8……………………………………………………………....Siphonognathus attenuatus
2b.  Segmented dorsal fin rays 10-13;  total dorsal fin rays 27-33; anal fin rays 8-12 (rarely 8)...................................................................................................................................................3.

3a.  Dorsal fin spines 15-16;  body moderately shallow, greatest depth 5.9-6.6 in SL; dorsal fin with deep notch between spinous and soft portions.............................Siphonognathus caninus.
3b.  Dorsal fin spines 16-21 (rarely 16);  body shallow to very shallow, greatest depth 6.9-12.8 in SL; dorsal fin without deep notch between spinous and soft portions (margin slightly concave in some juveniles)......................................................................................................................4.

4a. Body very shallow, greatest depth 10.4-12.8 in SL; predorsal scales not reaching forward to above preopercular margin..............................................................Siphonognathus beddomei.
4b.  Body shallow, greatest depth 6.6-7.7 in SL;  predorsal scales reaching in advance of rear edge of eye.......................................................................................................................................5.

5a. Predorsal scales reaching forward to above front edge of eye or beyond;  lateral line scales 38-42 (rarely 38); depth of caudal peduncle 1.6-2.3 times in length of caudal peduncle...... ..........................................................................................................Siphonognathus radiatus.
5b.  Predorsal scales reaching forward no farther than above centre of eye;  lateral line scales 35-38 (rarely 38); depth of caudal peduncle 2.6-3.7 times in length of caudal peduncle...... .......................................................................................................Siphonognathus tanyourus.