There isn't a consensus pronunciation for scientific names. I had Latin in high school, with a teacher from Italy, and so learned something pretty close to classical pronunciation. When I started working in museums no one understood me because I pronounced the names of genera "correctly".
Stygimoloch has Greek roots, but as the name of a genus is considered Latin, so the g would be hard and the o's of approximately equal value. I asked our dinosaur preparator a few minutes ago. He says STIJ-i-mah-luk (American English), which is what I would have guessed. Dougal Dixon's Dinosaurs offers STIG-i-mol-ugh.