I really don’t know.
Leon in Blade Runner " Tortoise, what’s that?"
If you must have the scientific answer:
"Well, actually, there’s a meaningful difference between tortoises and other turtles . All tortoises are in fact turtles—that is, they belong to the order Testudines or Chelonia, reptiles having bodies encased in a bony shell—but not all turtles are tortoises . If tortoises are turtles , why not just call all turtlelike creatures " turtle “?”