When this question was recently posted I voted to close it based on it being either too broad or primarily opinion-based. Take your pick.
The OP pointed out there is a lengthy history of "anatomically correct" questions that frequently ask for insight into the evolutionary possibility of mythical and/or fictional creatures.
Have I missed something in the FAQ? Are they actually on-topic? Or are they on-topic by default simply by their volume and the precedent they set?
If "How could X evolve?" questions are on-topic
Then I recommend we modify the FAQ to specifically say so as they are (insofar as I understand the rules) 100% opinion-based. I'm actually interested to see if someone can convince me they are not 100% opinion-based. To prove my point, I'm willing to post the question, "Anatomically-correct: how would a one-eyed, one-horned, flying purple people eater evolve?"
If "How could X evolve?" questions are off-topic
- We need to close a bazillion questions to remove the precedent.
- We need to close @Tres-2b's current bounty.