Here's a one-of-a-kind toy prototype made by Hasbro in 1997, part of a proposal for a line of Dinotopia toys. The skybax is fully posable, with flapping wings, gripping foot claws, and a removable saddle for the Will Denison action figure.
As it often happens with toy ideas, this one never got off the ground. The toy line was tied to a movie at Columbia Pictures that went far into development but never got green-lit.
Edit: In the comments, Drew pointed out a Jurassic Park toy with a remarkable similarity. I'm not sure, but it's possible that the JP toy came first and that they modded it out for the Dinotopia presentation.
Previously: Hasbro's proposed Dinotopia action figures