However, to create a living, breathing world, the Walking with Dinosaurs team had to know how dinosaurs actually behaved. Long, slender limbs mean the animal was agile, whereas heavy bones give support not speed. But anatomical evidence only goes so far towards fleshing-out the dinosaur. Dinosaurs have been extinct for a while but they must have exhibited at least some behaviour similar to species alive today. Therefore, although we must take great care with any comparisons, modern animals provide the best guide we have to the way dinosaurs may have lived.
Crocodiles share an ancestor with dinosaurs.
Now, crocodiles and alligators are not dinosaurs. They're not even descendants of dinosaurs like the birds. However, crocodilians and dinosaurs branched off from the same common ancestor. This was the 'archosaurs' or 'ruling reptiles' and the split happened at least 240 million years ago. At the very least, the earliest dinosaurs and the earliest crocodilians must have shared some characteristics.