I also needed to make four images about dino sexual behaviors and decided to start with the rex couple I maked in my love scene.

I suposse the theropod used bird style positions for copulate, but T-rex have the problem of weight. I think this can be a reasonable option: female lie on his abdomen and male is squat down. Thus, the male's weight is mainly suportted by the same male, counterbalancing head and tail.

As usual, lightwave scene and render