One thing that has always interested me about The Land Before Time is the original story. I mean this in the sense that it was not based off of an explicit preexisting book or fairy tale.
This seems to be rare for animated kids' films. Most of the Disney and Bluth canons, such as The Secret of NIMH, Snow White, Dumbo, come from preexisting stories. This even applies to famous animated films before these, like Watership Down, The Plague Dogs, and The Last Unicorn.
Am I wrong in thinking that a completely original storyline is unusual?