Clarias nigricans, a new species of clariid catfish (Teleostei: Siluriformes) from eastern Borneo

Clarias nigricans, new species, is described from the Mahakam River drainage in eastern Borneo. It belongs to the C. nieuhofii species group, which is distinguished from other Asian clariids in having a greatly elongated body with 87-108 dorsal fin rays, 74-91 anal fin rays, 74-82 vertebrae and confluent median fins. Clarias nigricans can be distinguished from other members of the C. nieuhofii species group in having a narrow snout (with an egg-shaped head when viewed dorsally), dark violet grey coloration with small white spots on flanks, a narrow head (11.7-12.3% SL), a relatively large distance between the tip of the occipital process and the base of the first dorsal fin ray (8.1-9.8% SL), and few large serrations on the anterior edge of the pectoral spine.