Where do you get nodosaurus in fossil fighters

After a certain amount of time in the game (and by "time" I mean progress in the plot), the info clerk will tell you about mysterious "mole holes" appearing in Rivet Ravine. You'll find a hole with a ladder going down in Tunnel #4 (the tunnel on the far right that isn't on the right wall... when you get to the "t" in the tunnel, go up/north... you'll find the hole from there). When you go down, you'll find yourself in a Secret Tunnel. A guy dressed up as a mole will see you, and tell you his brother is missing. Just follow the tunnel and you'll find the missing brother at the end... except there are a couple of puzzles you have to solve before you can get to him. There will be stone slabs that ought to give you a hint as to how to solve the puzzle, but if you don't want to go through figuring it out:
1st time, 1st puzzle: The tunnel splits into two paths. The paths are marked "X" and "O". Just go through the O tunnel 3 times in a row to move on to the next section.
1st time, 2nd puzzle: Again, you'll have to go through this tunnel 3 times to move on. Each time you go through, though, there will be a treasure box (it gets bigger each time you go through the tunnel! :D). DON'T open it! A) there's nothing in it, and B) you'll have to start over (having to go through the tunnel 3 times) if you do.
At the end, you'll find the guy's brother.
I typed all that so that you could get through the entire Secret Tunnel (and thus be able to find many more fossils, raising your chances of finding the fossils you want). Secret Tunnel has some fossils that can't be found anywhere else. The vivosaurs you can find (that I've found and can remember) are: Nodo, Megath, Brachio, Tricera, Chelon, and I think Zino.