Key to species of Dysomma and Dysommina in Taiwan

As mentioned above, Dysommina shares many external characters with Dysomma and is thus included in this key.

1A. Pectoral fin absent; about 2 rows of teeth on upper jaw......................................... D. dolichosomatum

1B. Pectoral fin present; 4 or more rows of teeth on upper jaw...................................................... 2

2A. Intermaxillary teeth present; uniserial teeth on dentary......................................................... 3

2B. Intermaxillary teeth absent; multiserial teeth on dentary........................................................ 6

3A. Anus anterior, trunk shorter than head length................................................................4

3B. Anus posterior, trunk much longer than head length............................................. D. opisthoproctus

4A. Two large compound teeth followed by row of 22–31 smaller ones on lower jaw......................... D. polycatodon

4B. Single row of 7 to 11 large compound teeth on lower jaw...................................................... 5

5A. Total vertebrae 137–139; total lateral-line pore 40–48....................................... D. taiwanensis sp. nov.

5B. Total vertebrae 119–130; total lateral-line pores 57–75.............................................. D. anguillare

6A. Anus anterior, just below pectoral fin...................................................................... 7

6B. Anus posterior, well behind pectoral fin.................................................................... 8

7A. Lower jaw projects beyond snout, not appressed to upper jaw when mouth fully closed; lateral line extends to 1/2 HL before the caudal-fin base.......................................................................... D. melanurum

7B. Lower jaw included, not projecting beyond snout, appressed to upper jaw when mouth fully closed; lateral line extends to about anterior 23% of body...................................................................... D. goslinei

8A. Five compound teeth on vomer; lateral-line pores present; head pores present on frontal, infraorbital posterior to eye and preopercular................................................................................. D. longirostrum

8B. Four compound teeth on vomer; pores absent onlateral line, frontal, infraorbital posterior to eye and preopercular............................................................................................... Dysommina rugosa