In fossil fighters can you find guan without a fossil chip in your sonar

I should think you'd be able to find any vivosaur without fossil chips... you just won't be able to find all 4 parts. You'll always be able to find head fossils, no matter what, and you'll always be able to find another kind of part (arms, legs, or body) without getting fossil chips. Getting the first fossil chip will let you find another kind of part, and the second will let you find all four parts.
Some vivosaurs are just harder to find than others... and there are some that can only be found after a certain amount of time (by "time" I mean progress in the game). Just keep looking, and you'll find the parts you need.