Things like colour and expressions are made up. I suppose humans have to relate things they don't know about to things they have seen before, hence the similarities to lizards and birds I suppose. But it isn't really the animation team's fault that humans don't know as much about dinosaurs as they would like. So really, considering that what the animation team had to work with was the current human perception of what dinosaurs are like, they did an amazing job, especially for the time it was released. The best animation in a film ever up till that point really.
I'm not certain of the timeline of dinosaurs, but I believe they were named as dinosaurs in the mid-19th century, which means "terrible lizard" in Greek. Really since then you have to think people have been trying to prove them as being very similar to lizards ever since then, when it was indeed their size that made them acquire their name. Really though, they are most likely wrong and we'll never know until there is some ridiculous new technology.
