This mission is like High Ptera, though instead of pesky pterodactyls, you have to deal with pesky Biosyn. There are still a few dinosaurs, but not very many, and you can generally just avoid them. The way to the scout is fairly linear and straightforward: just keep moving right, and always take the high road, advancing upward, when you have a choice. You'll likely have some good time to spare on the clock if you make it.
Use your rifle for most of the mission, but take out the flamethrowers with either the machine gun or shotgun as appropriate. The flamethrowers here can be really nasty, so be careful. Sometimes you must drop to a platform with a flamethrower on it. In that case, equip the shotgun, drop to the far left of the platform, duck, and quickly fire a few shots to get rid of him as fast as possible in case he's able to hit you with his flames. If you're lucky, he'll shoot over your head and you'll escape unscathed.
After you exit the second cave, you'll notice a platform below you to the right. Very quickly run to it and drop down on the far left before a flamethrower walks up too close to the edge, and quickly dispatch him. Otherwise, you might have a rough time dispatching him. If he advances too far to the edge before you can jump down on the platform, just duck back into the cave and back out, and you can try again.
Toward the end, you'll be in a cave where it's a long downward slope, followed by a door, then a long upward slope, with gunmen all along the way. Ignore this first door and go into the door at the top of the upward slope. Afterward is the last segment of the level, which is pretty straightforward.