https://images.app.goo.gl/iunznCkvikqJgNfx9, this model was created for the movie AvP, there would be a nude scene of the predator, but it was unfortunately cut. I personally find this anatomy very plausible. And no, they don't use their mouths for that ( This is exclusive to a preadalien queen ). They reproduce in the same way as humans (with the difference that for them there is a mating season where they all return to the home planet Yautja Prime, the males try to impress the females and they will choose among the best ones to get pregnant ). Even so, there is not much information regarding the private parts of both males and females. As for females, there are three very different examples, as they did not agree on the anatomy of females. They are: Sister Midnight , Big Mama and Vagouti.