It's a male. My guess is that this is a tank-bred fish? It looks like what most would call a turquoise severum, but I'm still confused because some places show it as a separate and valid species still (Heros appendiculatus) and others say it's been combined with the green severum, Heros efasciatus. If it's a tank-bred fish, there's always the chance it's just a mix. Either way, he looks to have pretty nice markings. He'll look even better in a couple weeks when he settles in.
I wouldn't call it Heros sp. Santarem unless you knew for certain that it was a wild fish caught in that region. Unless it has unique features like the Inirida or rotkeil types, it's probably hard to say that it's this or that unless you know where the fish came from.