Well, there's a song I was thinking of when I was painting them about the unicorn being the most beautiful animal, but how all of them were left behind when the ark set sail. I can't remember what the song was called or who it was by, but what I vaguely remembered inspired me.
Only I figured I would add dinosaurs into the mix. So yes, to answer your question, the dino and the unicorn were left behind. I figured it was kind of sad, so I tried to make the rest extra cute to make up for it. Consider it an ode to some of earth's coolest extinct animals.