Abstract
Barilius signicaudus, a new species of cyprinid fish from the Khwae Noi and Khwae Yai branches of the Maeklong River,
western Thailand, is described. It is characterized by the combination of a large, elongated blotch at the caudal-fin base
(blotch is formed by the fusion of the large caudal spot at the fleshy end of the caudal base and the last vertical bar on the
flank) that extends about 1/3 of the distance from the caudal-fin origin beyond the last scale on the caudal base to the margin
of the caudal fork; an anal-fin origin opposing the 2nd–4th branched dorsal-fin rays; eight scale rows above the lateral
line; dark pigment on the dorsal fin concentrated mainly along the margins of the rays; 36 or more precaudal lateral-line
scales; and small dentary tubercles. This species has previously been identified as Barilius pulchellus and Barilius ornatus.
Barilius pulchellus has no, or a small caudal spot, a dorsal fin with dark pigments concentrated in the middle of the
interradial regions, and much larger dentary tubercles. Barilius ornatus and similar species have an anal-fin position that
opposes the 5th–7th branched dorsal-fin rays (rarely the 4th), or does not overlap with them at all, and have no, or small
caudal spots.