It's such a shame that we have so few fossils. When you really start thinking about it, many dinosaurs have very distinct and memorable characteristics and would make great Pokemon designs. The one that I would personally like to see the most is stegosaurus (pic related), but there many other cool ones, such as:
Spinosaurus:
http://prehlife.weebly.com/uploads/2/2/0/8/22089980/296866555_orig.png?516And
Ankylosaurus:
http://ichef.bbci.co.uk/naturelibrary/images/ic/credit/640x395/a/an/ankylosauria/ankylosauria_1.jpgAssuming that they'd all have to be Rock-type, I'd do something like this:
>Stegosaurus: Rock/Grass, slow bulky physical attacker with all kinds of moves related to spikes/stinging (Pin Missile, Twineedle, Spike Cannon etc.)>Spinosaurus: Rock/Dark or Rock/Fighting, really fast and hard hitting physical attacker with mediocre/low defenses>Ankylosaurus: Mono Rock, high attack and REALLY high defense but low special stats and speed, learns all kinds of moves related to hammering/mauling (Hammer Arm, Wood Hammer etc.) 