A new species of congrid eel genus, Ariosoma is described here based on two mature female specimens collected from trawl by-catch landings at Thoothukudi fishing harbour, off Thoothukudi, Bay of Bengal. The new species can be easily distinguished from its congeners in having pre-anal length 48.7–49.1% TL; dorsal-fin origin just before pectoral-fin insertion; body bicoloured, pale brown dorsally and silvery white ventrally; preopercular portion dark; pectoral fin reddish with dark spot at the base; SO canal with six pores; pre-dorsal vertebrae 10–11; pre-anal vertebrae 61–64; total vertebrae 162–163. Further, the new species differs from all the congeners of Indian waters in having more total vertebrae, except A. albimaculatum (162–163 vs 129–153 in others; 161–164 in A. albimaculatum). The new species identity was also supported by molecular analyses using the mitochondrial COI gene and the result revealed that the new species is closely related to Ariosoma maurostigma and Ariosoma albimaculatum with a pair-wise genetic distance of 11.4% and 11.6% followed by A. melanospilos with 16.8%.
