"A young turtle is crawling on the ground by the sea."

Translation: Egy fiatal teknős mászik a földön a tenger mellett.

[Jonaskat87]

Why is "teknősbéka" incorrect in place of "teknős"? I put "teknősbéka," and it said that it was wrong. I mean, I know that "teknős" works as well, but I still don't see the issue.