BOF,
Dinosaurs are nothing more than reptiles, and were created with the other reptiles on the 6th day (IIRC). One thing to consider, without going into too much detail here (perhaps in another thread or email), the atmospheric conditions of the earth at it formation are not the same as today. Serious changes on a planetary and intersolar level occurred at the flood, that coinside with the 40 days of rain.
Because of the conditions before the flood, reptiles, which grow all their lives, had an environment where they could live for centuries, continuously growing. They became dinosaurs. Today, there is not enough atmospheric pressure and oxygen to allow reptile to grow such enormous sizes.