Dysomma melanurum Chen & Weng, 1967

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 : 96-98

Dysomma melanurum Chen & Weng, 1967

Figs. 6 A–B; Table 2

Dysomma melanurum Chen & Weng, 1967:84 , fig. 63 (Type locality: Tungkang [Dong-gang], Taiwan). Chen & Mok, 2001:79. Ho et al. 2010:26. Ho & Shao, 2011:22 .

Specimens examined. Lectotype: NMMB-P5284 (formerly THUP 1687), Tungkang [Dong-gang], SW Taiwan.

Paralectypes: NMMB-P3885 and NMMB-P5470, same as lectotype. Non-types: collected from Dong-gang, SW Taiwan by midwater trawl: NSYU 2732 (1, 237 mm TL). NMMB-P3885 (1, 191, partly dry), 13 Feb. 1962. NMMB-P10949 (3, 271–285), 4 Sep. 2010. NMMB-P11122 (2, 258–261), 13 Sep. 2010. NMMB-P13741 (1, 265), 29 Jul. 2011. NMMB-P13841 (1, 260), 5 Oct. 2010. NMMB-P14044 (7, 206–285), 3 Nov. 2011. NMMB-P14213 (1, 255), 20 Oct. 2011. NMMB-P15471 (3, 281–297), 2 Jul. 2011. USNM 398473 (1, 165), 13 Nov. 2009. USNM 398474 (1, 178), 13 Nov. 2009.

Diagnosis. Pectoral fin present; dorsal-fin origin above middle of pectoral fin, predorsal length 11.5–15.0% TL; lower jaw longer than upper jaw, slightly curved and not appressed to upper jaw when mouth closed; anus anterior, below pectoral fin, preanal length 15.4–17.3% TL; trunk very short, trunk length 3.0–5.3% TL; no intermaxillary teeth; multiple rows of teeth on upper jaw, those on innermost row about twice the size of the rest; 5 or 6 (mainly 5) compound teeth on vomer; multiple rows of teeth on lower jaw, those on innermost row about twice the size of the rest; head pores: IO 4, SO 3, M 7 (1 with 8), POP 0, AD 1, F 0, ST 0. Lateral-line pores very large, predorsal 10–13, prepectoral 8–11, preanal11–17, total pores 107–117, the last to 1/2 HL before the caudal-fin base. MVF 13-14-135, total vertebrae 131–138. Body uniformly light pinkish to grayish with numerous melanophores, posterior margin of anal fin and caudal fin black.

Remarks. This species has a very different morphology of its lower jaw, strongly curved and not appressed to the upper jaw when the mouth is closed. This may reflect its pelagic living. Many specimens are found to feed on pelagic shrimps. This is a small species; the largest specimen examined was only 297 mm TL.

Robins & Robins (1976:263) suggested that the projecting lower jaw of this species was an artifact, based on the damaged condition of the specimen they examined (THUP 1687, now the lectotype). We have examined 25 specimens, however, and they all have a clearly projecting lower jaw.

Figures

FIGURE 6. Dysomma melanurum Chen & Weng, 1967. NMMB-P 10949, 2 of 3. A. 285 mm TL. B. 271 mm TL.