From what I've heard so far, the story is about a baby apatosaurus who gets his home destroyed. He then assumedly heads out to find a new one.
There doesn't seem to be any characters except him and his short-lived father. Why are there 4 other characters on the front cover?
Sorry, but that information is not correct.
As for the characters in the movie, you can forget those you see on the cover, they are much better looking (!) than what you get to see in that movie.
I haven't watched that movie since I got it in early 2004. The main character (I think his name was Tio) is impossible to ascribe to any kind of dinosaur species. His parents (both of them appear in the movie and both of them life to see the end of it) remotely resemble Iguanodons, but it really takes a lot of good will to identify them as such.
The other main character of the story is Cree, the Petrie like creature you saw in one of the pictures. There are a couple of other characters, but I don't recall the names.
The story is really very strange and involves a dinosaur building a seismograph and caves with torches hanging on all the walls (though there is no reference where those torches are coming from). Apart from quite a few subplots the main plot is about the main character and some others being separated from their parents after a big volcanic eruption. After a long quest they find back to their parents.
The animation of the movie is truly dreadful.
There were a couple of funny dialogues and a few ideas which were somewhat interesting, but the realization of those ideas was really poor.