Dysomma

Ho, Hsuan-Ching, Smith, David G. & Tighe, Kenneth A., 2015, Review of the arrowtooth eel genera Dysomma and Dysommina in Taiwan, with the description of a new species (Anguilliformes: Synaphobranchidae: Ilyophinae), Zootaxa 4060 (1), pp. 86-104 : 102-103

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