Diagnosis: The original description by Carl Hubbs offers a detailed comparative diagnosis of Paratheraps synspilus against the Vieja maculicauda. Four traits are identified; 1) The body is slightly slenderer. 2) The contours are less globose. 3) The dorsal, anal and pelvic fins are not so sharply pointed nor so produced. 4) The black caudal blotch is longer (nearly as long as head).
P. melanurus differs from Paratheraps synspilus in the “downward slope in the caudal band” (Hubbs, 1935), in P. melanurus being straight pointing horizontally to the eye while in P. synspilus has a slight downward angle pointing directly to the chin.
For Paratheraps bifasciatus (Steindachner, 1864), coloration and marking diagnosis includes a defined black blotch on the operculum to which the horizontal caudal band points. This blotch is just faintly visible in some adult individuals of Paratheraps synspilus. P. bifasciatus also has a defined “second” horizontal black band (which gives it the specific name) between the caudal band and dorsal fin base, widening into a blotch in its middle part and running from the base of the caudal fin to the opercular blotch. In some cases this second bar actually fuses with the caudal band, which in P. bifasciatus, unlike Paratheraps synspilus, extends father frontward (at least to the middle part of the dorsal fin) and in many cases (in particular in younger individuals) to the opercular blotch. Paratheraps bifasciatus also has a distinctive reticulated color pattern on the head, which varies in extension in populations but it is always visible on the cheeks (Artigas Azas, 2008).
