The easiest way to catch a Styracosaurus is to go into the woods where there are still swamp plants. This is where they usually lay there nests. Once you have found one shoot it once. It wil take a few hits to kill with only a Tranqulizer. Get it to charge you then run away from it backwards with it facing you. That way you can have a straight shot at it.
Easy Way To Capture A T-Rex
The easiest way to capture a T-Rex is to use the call box and the 9mm Rail Gun. Set the call box in a wide open space then back up some. Usually if it works a whole bunch of T-Rex will come. If you have the invincebility code you can have your pick of the bunch. Make sure and use the 9mm Rail Gun because one shot will take them down. One shot
is useful because once they get there they like to run really fast and it's hard to get a shot in.