Kryptopterus geminus

description

Description. Body laterally compressed; maximum body depth located immediately anterior to pelvic-fin origin; head as broad as body and moderately depressed. Dorsal profile of body horizontal to very slightly convex, without nuchal concavity. Anterior profile of snout rounded. Anterior pair of nostrils tubular and anteromedial to maxillary barbel base. Posterior pair of nostrils bordered by fleshy dorsal and ventral membranes and posteromedial to maxillary barbel base. Mouth terminal; gape oblique, moderate and extending to midway between maxillary barbel base and anterior orbital margin. Well-developed rictal lobes present, subtended by deep submandibular groove. Thin, broad supralabial fold extending from below orbit to point two thirds of way between maxillary barbel base and anterior orbital margin. Jaw teeth depressible and villiform. Premaxillary teeth in 4 - 5 irregular rows in narrow, gently curved rectangular bands. Dentary teeth in similar, slightly narrower bands narrowing posterolaterally, reaching from symphysis almost to mouth corners. First row of dentary teeth slightly visible when mouth is closed. Vomerine teeth in 2 - 3 rows in single crecentic band straddling mid

Kryptopterus geminus, a new species of silurid catfish (Teleostei: Siluridae) from mainland Southeast Asia.

diagnosis

Diagnosis. Both K. cryptopterus and K. geminus can be distinguished from congeners in the dorsal profile lacking a nuchal concavity (vs. nuchal concavity present) and having short maxillary barbels (extending to the base of the pectoral fin vs. extending beyond tip of pectoral fin). Kryptopterus geminus differs from K. cryptopterus in having a narrower head (9.5 - 12.0 % SL vs. 12.2 - 14.2), longer anal fin (62.2 - 72.7 % SL vs. 57.2 - 62.9) and snout (39.5 - 45.3 % HL vs. 35.1 - 39.8), and more laterally-placed eyes (only ventral half of the orbital margin visible when the head is viewed ventrally vs. ventral two-thirds; Fig. 2).

Kryptopterus geminus, a new species of silurid catfish (Teleostei: Siluridae) from mainland Southeast Asia.

discussion

Discussion Both K. cryptopterus and K. geminus can be distinguished from all other silurids in possessing the following two synapomorphies: a supralabial fold that is anteriorly truncated such that the lower edge extends far posterior to the base of the maxillary barbel and an elongate antorbital process of the lateral ethmoid that is not anteroposteriorly compressed (Bornbusch, 1995). Kryptopterus geminus and K. cryptopterus also do not show any marked sexual dimorphism in the pectoral-fin spine as reported for most other silurid genera (e. g. Inger & Chin, 1962; Bornbusch & Lundberg, 1989; Ng & Ng, 1998). The two species are further distinguished from congeners in lacking a nuchal concavity (present in all other Kryptopterus) and short maxillary barbels (reaching to base of pectoral fin vs. reaching at least to the origin of the anal fin in congeners).

Kryptopterus geminus, a new species of silurid catfish (Teleostei: Siluridae) from mainland Southeast Asia.

discussion

The differences noted between K. cryptopterus and K. geminus are not due to ontogeny. Bivariate analyses (ANCOVA) of the regression lines of the anal-fin length, head width and snout length on SL for both species are significantly different at P <0.000005 (Fig. 4). The identity of the material identified as K. cryptopterus by Smith (1945) from the Tapi River drainage could not be ascertained. It is very likely that it may represent K. geminus, given the similarity of the fauna from the Tapi River drainage with that of the Mekong.

Kryptopterus geminus, a new species of silurid catfish (Teleostei: Siluridae) from mainland Southeast Asia.