本文根据采自海南岛的标本描述了中国南海一新记录种:颈斑尖猪鱼(Leptojulis lambdastigma)。本种的主要形态特征为:体长形,体长为体高的3.7~4.0倍,为头长的3.1~3.6倍;头长为吻长的2.7~3.3倍,为胸鳍长的1.45~1.65倍:头裸露无鳞;两颌前端各具2对大犬齿,外侧1对犬齿弯向外后方;背鳍Ⅸ-12,臀鳍Ⅲ-12,胸鳍i(不分支)+11-12(分支);侧线完整,侧线鳞27;颈部具一个“V”形大黑斑,胸鳍后部的上方、侧线的下方具一小黑斑。新鲜标本头部具2条黄色纵带,沿体侧分别经眼和胸鳍基部向后达尾鳍基部;体侧背部具1条浅棕黄色条带;胸鳍基部棕红色,后部浅色;臀鳍浅蓝色:尾鳍下部淡蓝色,上部橙色。本种与尾斑尖猪鱼(L.urostigma)形态较为相似,主要差别在于颈斑尖猪鱼的颈部具有一显著的“V”形黑斑,尾鳍基部无黑斑(尾斑尖猪鱼具此黑斑)。
Leptojulis lambdastigma, new to the South China Sea, is identified from a specimen collected from the Hainan Island. Diagnostic characteristics for this species as follows: body moderately elongate, the depth 3.7 - 4.0 in standard length (SL), head length 3.1 - 3.6 in SL; snout length 2.7 - 3.3 in head length (HL), pectoral fins 1.45 - 1.65 in HL; head naked; 2 pairs of canine teeth anteriorly in both jaws, the second pair recurved and outcurved. Dorsal fins Ⅸ-12, anal fins Ⅲ-12, pectoral fins i (unbranched) +11 - 12 (branched); lateral line complete, and lateral-line scales 27; a large V-shaped dark mark on nape; an irregular black blotch below lateral line above pectoral fin. Color when fresh with 2 yellow stripes on sides of head, the first from upper lip through eye to end of the basal part of caudal fin, the second beginning at comer of mouth, passing the basal part of pectoral fins and extending to the basal part of caudal fin; one faintly yellow stripe on the back near to dorsal fin; pectoral fins brown to red anteriorly, and pale colours posteriorly; anal fins pale blue; lower and upper parts of caudal fin separated, slight blue and orange. Color of preserved in formalin is significantly different from the fresh specimen, body with a pale color, and the stripes disappeared except for the V-shaped dark mark. It differs from the similar L. urostigma in: nape with the V-shaped dark mark (absent in L. lambdastigma), and without the dark blotch at base of caudal fin found in L. lambdastigma. L. lambdastigma has been recorded from Gulf of Thailand, Philippines, Malaysia, and Taiwan of China to date.