why does the greater petrosal nerve enter the pterygoid canal?

[Xalatan]

Why not just use foremen rotundum to access pterygopalatine ganglion?

Edited December 24, 2015 by Xalatan

[Function]

My best guess would be that it's already occupied by the maxillary nerve (V2 < N. V, trigeminal nerve), since the round foramen itself isn't very large, I think. Exceptional is the jugular foramen, which holds passage for IX, X and XI, but that one's not very small so that doesn't form a genuine problem.