Echelus

Ho, Hsuan-Ching, 2015, New species of the snake eels Echelus and Ophichthus (Anguilliformes: Ophichthidae) from Taiwan, Zootaxa 4060 (1), pp. 71-85 : 72-73

Key to the Taiwanese species of Echelus and Ophichthus

Note: Taiwanese species of Ophichthus include those for which we have examined specimens as well as O. fasciatus and O. stenopterus whose presence in Taiwan is not verified.

1A. Tail tip flexible, caudal-fin rays covered by skin, but confluent with dorsal and anal fins......................2 ( Echelus )

1B. Tail tip a hard or fleshy finless point............................................................ 3 ( Ophichthus )

2A. Posterior membrane of dorsal and anal fins blackened ca. 1 head length (HL) before tail tip; head length (HL) 8.3–8.7 in total length (TL); total vertebrae 150–162............................... Echelus uropterus ( Temminck & Schlegel, 1846)

2B. Posterior membrane of dorsal fin clear, anal fin blackened ca. 1 HL before tail tip; HL 12.0– 13.1 in TL; total vertebrae 172– 183......................................................................... Echelus polyspondylus sp. nov.

3A. Body coloration markedly spotted or with distinct dark saddles; dorsal-fin origin (DFO) above gill openings, in advance of pectoral-fin tips; pectoral fins rounded, not elongate..........................................................4

3B. Body coloration uniform or with irregular brown blotches, darker dorsally, without distinct spotting or distinct dark saddles; DFO above or behind pectoral fins; pectoral fins rounded or elongate............................................ 8

4A. A dark brown or black saddle on posterior half of head; body brown, without spots or saddles............................................................................................... Ophichthus cephalozona Bleeker, 1864

4B. Head lacks a single broad dark dorsal saddle; numerous dark spots or saddles on body............................... 5

5A. Body overlain with 18–27 prominent dark saddles............................................................ 6

5B. Body overlain with numerous dark or ocellated spots, those spots not appearing as saddles........................... 7

6A. Tail length 1.6–1.7 in TL, longer than head and trunk; dorsal-fin origin above mid-pectoral fin; numerous golden to brown (in life) marblings on snout and face; total vertebrae 156–164......................... Ophichthus bonaparti ( Kaup, 1856)

6B. Tail length 2.1 in TL, slightly shorter than head and trunk; dorsal-fin origin above gill opening; face and snout lack pale mar- blings; vertebral count unknown....................................... Ophichthus fasciatus ( Chu, Wu & Jin, 1981)

7A. Head and body overlain with numerous ocellated spots, those on body in 3 regular alternating rows, the spots separated by pale interspaces; total vertebrae 141–148...................................... Ophichthus polyophthalmus Bleeker, 1864

7B. Head and body overlain with numerous dark spots, those on body in 2 or 3 irregular rows, the spots about equal in size to their interspaces; total vertebrae 151–160..................................... Ophichthus erabo ( Jordan & Snyder, 1901)

8A. DFO more than 1 pectoral-fin length behind gill openings..................................................... 9

8B. DFO in advance of, above, or behind gill opening by no more than 1 pectoral-fin length............................. 11

9A. DFO behind gill opening by more than 3 pectoral-fin lengths; total vertebrae 158–163.... Ophichthus megalops Asano, 1987

9B. DFO behind gill openings by less than 3 pectoral-fin lengths.................................................. 10

10A. DFO behind gill opening by the length of the pectoral fin; body moderately elongate, its depth 25–38 in TL; teeth biserial on jaws, uniserial on vomer; dorsal fins and pectoral fins dark; total vertebrae 158–163................................................................................................ Ophichthus aphotistos McCosker & Chen, 2000

10B. DFO at least 2 pectoral-fin lengths behind gill opening; body stouter, its depth 25–31 in TL; teeth biserial anteriorly on vomer and maxillary, uniserial on mandible; all fins pale; total vertebrae 155–163.................. Ophichthus bicolor sp. nov.

11A. Dorsal surface of trunk and tail overlain with brown irregular blotches, ventral surface distinctly pale; dorsal surface of head and gill basket brownish-black; DFO above mid-pectoral fin; pectoral fins elongate, not pointed; teeth uniserial; total vertebrae 148–153...................................................... Ophichthus lithinus ( Jordan & Richardson, 1908)

11B. Dorsal surface of head and trunk tan to brown, lacking irregular blotches; head lacks a dark nuchal band; DFO location vari- able, above or slightly behind pectoral fins; pectoral-fin shape variable; teeth uniserial or biserial..................... 12

12A. Vomerine teeth biserial; body elongate, its depth more than 40 times in TL; 2 preopercular pores (POP)................ 13

12B. Vomerine teeth uniserial; body moderately elongate, its depth less than 40 times in TL; 2 or 3 POP.................... 14

13A. DFO above or slightly behind posterior tips of pectoral fins; all teeth biserial; total vertebrae 169–173........................................................................................... Ophichthus stenopterus Cope, 1871

13B. DFO behind pectoral fin by length of pectoral fin; teeth biserial on vomer, uniserial and becoming biserial on jaws; total verte- brae 207–218........................................................... Ophichthus macrochir ( Bleeker, 1852)

14A. Pectoral fin rounded, spatulate, or short and pointed, not elongate, its length less than or equal to jaw length............. 15

14B. Pectoral fin elongate, pointed, its length greater than jaw length................................................ 18

15A. Tip of lower jaw extends beyond anterior nostril bases; DFO slightly before or behind end of pectoral fins; total vertebrae 133– 141...................................................... Ophichthus urolophus ( Temminck and Schlegel, 1846)

15B. Tip of lower jaw does not reach anterior end of bases of anterior nostrils; DFO above pectoral fins.................... 16

16A. Tail tip blunt; pectoral fin less than jaw in length; rear margin of orbit well ahead of rictus of jaw; total vertebrae 127–132.................................................................... Ophichthus asakusae Jordan & Snyder, 1901

16B. Tail tip pointed; pectoral fin equal to or slightly longer than jaw; rear margin of orbit above or slightly behind rictus; vertebrae 148–164............................................................................................ 17

17A. A prominent down-pointed slender barbel behind base of anterior nostril; median fins pale; snout 21–28% of head length; vertebrae 155–164................................................................... Ophichthus shaoi sp. nov.

17B. Lip barbels thickened, not slender and pointed; median fins dark; snout 14–21% of head length; total vertebrae 148–159.................................................................. Ophichthus obtusus McCosker, Ide & Endo, 2012

18A. Dorsal fin with a dark margin; pectoral fins brownish-black; 3 POP; teeth uniserial; total vertebrae 171–182...................................................................................... Ophichthus altipennis ( Kaup, 1856)

18B. Dorsal-fin margin not notably darkened along body and majority of tail region; pectoral fins pale; 2 POP; vomerine teeth biserial anteriorly or centrally, maxillary teeth uniserial; total vertebrae 141–161...................................... 19

19A. Head 9.0–9.5 times in TL; eye 3.0–3.5 times in upper jaw, 14–16 in HL; small barbels along lip behind anterior nostril and beneath mid-orbit; total vertebrae 141–146................................... Ophichthus apicalis ([ Bennett], 1830)

19B. Head 10–12 in TL; eye 2.3–2.4 in upper jaw, 7.3–11.3 in HL; 1 small barbel along upper lip behind anterior nostril, none beneath mid-orbit; total vertebrae 146–161......................... Ophichthus machidai McCosker, Ide & Endo, 2012