Hypoptopoma inexspectata is diagnosed and redescribed based on the examination of additional
material and comparison with its congeners. This poorly known hypoptopomine species is distributed in the
Paraguay and Paraná river draínages. Hypoptopoma inexspectata is diagnosable based on the
autapomorphy biserial arrangement of anterior snout rostral margin odontodes, laterally extended to limit
between second and third infraorbital plates, with dorsally directed dorsad series separated from ventrally
directed ventrad series by a narrow odontode-free area, which at the level of first and second infraorbital
plates is reduced to a dividing line of the series. The species can be further distinguished by the
combination (1) low number of canal-bearing lateral plates (20-22, typically 21), (2) presence of a shield of
prepectoral dermal plates, (3) arrangement of abdominal plates in one paired series of 3-5 plates, (4)
shorter least interorbital distance 4856% head lengh, (5) larger horizontal eye diameter 17-20% head lengh,
and (6) least orbit-nare distance 812% head lengh. Intraspecific variation skull dermal bones, neuracranium
and suspensorium bones, dermal plates, adipose fin is reported. (PDF has 20 pages.