Mike T: What's 4+4? Mike K: [Considering that 4+3 is a more interesting question] 7 Mike T: OK, great! I have two four-panel walls to cover, and now I know that I need to buy seven panels.
That's not a fair analogy. Answering the question of why no non-ornithuran pan-avians became aquatic effectively answers why no non-avialan dinosaurs became aquatic, the latter being a subset of the former. Answering the question of what is 4 + 3 does not in any way answer what is 4 + 4. -- Mike Keesey