Itaituba is not really a scientific name. It's the name of a city placed at the banks of the Rio Tapajos, which is not far away from the place this rays are coming from.
In my opinion it is not really unusual, to name not exactly known species or variants of known species like a bigger city next to the place they have been caught......like Pot. leopoldi from Sao Felix do Rio Xingu for example.
Regards
Stefan