I’ve been looking for this ever since they cracked most species DNA.
Biological engineering. There was a serious of sci-fi books I read years ago about a race of intelligent dinosaurs sharing Earth with humans, and the dinosaurs had perfected bioengineering. They made a ship out of a giant plesiosaur that had a air chamber they could carry passengers and cargo in, among other things.
West of Eden by Harry Harrison.
https://en.wikipedia.org/wiki/West_of_Eden
Clayface from Batman comes to mind.
Did they take humans along for snacks?