Paracetopsis esmeraldas Vari, Ferraris & de Pinna, 2005
Identification: Paracetopsis esmeraldas is distinguished from all other species in the Cetopsinae with the exception of P. bleekeri and P. atahualpa by the combination of the possession of a vomerine tooth patch with more than one row of teeth and a medial separation of the contralateral components of the patch. Paracetopsis esmeraldas differs from P. atahualpa and P. bleekeri to a notable degree in the number of total vertebrae (50 to 53, with 22 of 26 radiographed specimens having 51 to 53, vertebrae versus 50 in P. atahualpa, and 47 to 50, with 50 in only 1 of 21 radiographed specimens in P. bleekeri). Paracetopsis esmeraldas further differs from P. atahualpa in the dorsal profile of the body at the rear of the head in the area of contact of the externally apparent posterodorsal portion of the jaw musculature and the anterior portion of the epaxial musculature (without distinct notch versus with distinct notch, respectively), the degree of pigmentation of the basal portion of the maxillary barbel (pale or with few scattered, dark chromatophores versus distinctly dark, respectively), and to a degree in the number of caudal vertebrae (37 to 40, with 38 most common, versus 36 to 38, with 37 most common, respectively). Paracetopsis esmeraldas further differs from P. bleekeri in the extent of t he medial gap in the vomerine tooth patch (separated by a limited gap between the contralateral components of the tooth patch equivalent to the width of one or two vomerine teeth versus separated by a distance equivalent to the width of three or four vomerine teeth, respectively), in the pigmentation on the lateral surface of the opercle (patch of dark pigmentation present versus absent, respectively), and in the mode and to a degree in the range of the number of caudal vertebrae (37 to 40, with 38 most common, in P. esmeraldas versus 34 to 38, with 36 most common, in P. bleekeri). Maximum size: 188 mm SL.
Range: Paracetopsis esmeraldas occurs in the Pacific Ocean versant rivers of northwestern Ecuador.
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.