User blog comment:LordHelix990/Prehistoric Past/@comment-25118285-20160912192216

Some things to consider:

If you're going to be having extremely obscure animals in your novel, how are these 5 random teens going to know what they are? How would they know and identify what an erketu is?

You have quite a long list here; if you intend on having them all featured, make sure the island you're writing about has enough SPACE for all of them, and habitats! And make sure that it makes sense that your five teens are able to traverse such a large area in order to able to see all these things!

When you have an animal as a "villain," make sure you don't lose sight of the larger conflict - which, in this case I'm guessing is escaping the island.

If you're including aquatic and avian animals, make sure you come up with a logical reason for them staying around the island. What's to stop a quetz from flying to the next land mass, or the liopleurodon from swimming away?

Lastly, I'd suggest drawing a crude map. Because A) you will need to be able to remember where they are in relation to landmarks and herds and habitats, and B) plotting where you want certain animals and how big their populations should be can effect what you choose to include in the end.