They used Dinos because they couldn't use Apes.THE DINOSAUR ONE! Crap, I had forgotten all about that. That one might actually have been worse than Threshold. No, wait, Tom Paris pulled out his tongue. Lizard babies. No, Threshold was still worse. But the Dinosaur one was a Very. Close. Second.
Ah, c'mon! Distan Origin is one of the best Voyager Episodes. Yes the Dinosaur part is a bit silly but the episode itself, besides being quite fresh by telling the story mostly from the point of view of the Voth scientists and with great make up/visual effects/direction/acting/continuity, is a very interesting and compelling analogy in the great tradition of Star Trek...
"Distant Origin" is paying homage to "Planet of the Apes"
Remember Dr. Zaius didn't want the mass population to know about the cave with the baby doll because it would prove man came first, they were related as a species and was intelligent. He feared the knowledge would destroy the foundation of the life apes lived. So he exiled Charlton Heston and put Zera into scientific obscurity to keep the secret safe .