Denticetopsis macilenta (Eigenmann, 1912)

Identification: Denticetopsis macilenta is distinguished from D. royeroi and D. sauli by the combination of the lack of elongate, symphyseal teeth on the dentary, the lateral line extending posteriorly on the body beyond the abdomen at least onto the caudal peduncle, the presence of dentition on the vomer, a dorsal fin with 5 or 6 segmented rays and with a first ray which is spinous basally, a symmetrical, shallowly-forked caudal fin, and the possession of horizontally-elongate, stellate, dark chromatophores when the chromatophores are expanded. Denticetopsis macilenta differs from D. epa in the proportional length of the pelvic fin (reaching just anterior of the anterior margin of the vent versus to the posterior margin of the vent, respectively) and in the relative position of the eye (located at anterior 0.18-0.19 of HL versus 0.25 of HL, respectively). Denticetopsis macilenta differs from D. praecox in the relative position of the eye (located at anterior 0.18-0.19 of HL versus 0.25-0.26 of HL, respectively), the number of irregular rows of teeth on the median portions of the premaxilla (three versus two, respectively), in the profiles of the postorbital portion of the head from a dorsal view (convex versus approximately straight, respectively), and in the width of the head as a proportion of the length of the head (head width/HL 0.77-0.84 versus 0.71-0.74, respectively). Denticetopsis macilenta differs from D. iwokrama in the number of caudal (28 to 30 versus 32), preanal (14 to 16 versus 17), and total vertebrae (40 or 41 versus 43), the position of the middle of the orbit (located at anterior 0.18-0.19 of HL versus 0.25 of SL, respectively), and in the width of the head as a proportion of the length of the head (head width/HL 0.77-0.84 versus 0.72, respectively). Denticetopsis macilenta differs from D. seducta in the position of the middle of the orbit (at anterior 0.18-0.19 of HL versus 0.25-0.27 of HL, respectively) and in width of the head as a proportion of the length of the head (head width/HL 0.77-0.84 of HL versus 0.61-0.70 of HL, respectively). Maximum size: 68 mm SL.

Range: Denticetopsis macilenta is only known from a limited area in the Potaro River basin of northern Guyana.

Information from Vari, R. P., C. J. Ferraris Jr. & M. C. C. de Pinna. 2005. The Neotropical whale catfishes (Siluriformes: Cetopsidae: Cetopsinae), a revisionary study. Neotropical Ichthyology 3:127-238.