Originally Posted by osromatra
I don't think mollies and platies will have viable offspring. They are totally different genus. It might happen, but it would be rare, and not something I'd count on.
it'd be like trying to mate a human with a chimp or gorilla: there are stories of viable offspring, but those are mostly folklore or anecdotal in nature, and can't be taken seriously without backing evidence. mollies and guppies are both members of the genus Poecilia and therefore can have viable, though usually sterile, offspring, much as a modern human and, say, a neanderthal or possible Homo erectus could, were either of them still alive.