Using biogeography to guess at species identity

Just over a week ago, I found two Corydoras habrosus mixed in with the Otocinclus at the local Petsmart. Since C. habrosus is restricted to the Amazon basin, it struck me as a useful clue in trying to identify the Otos. In his 1993 monograph on the genus Otocinclus, Scott Schaeffer mentions that only two species of Otocinclus are found in the Orinoco basin - O. vittatus and O. huaorani. I'm leaning a little more towards O. vittatus, but I really need to take a better look at them.