I regret to report that there is surely no such thing as a fish.[0]
replies(2):
"Only cladistically" is a bit like saying "only in reality" imo. :P
> As far as I understand, at least the common ancestor of all fish was still a fish.
Well.. eel-like probably more I'd guess. But yea.
The issue with "fish" is that people want it to be cladistic (trout and shark are fish) AND function (whales are not fish), and potentially also another anti-function (eels are not fish). You can't have it both/all three ways.
With crabs and trees that's 100% function, and that's fine imo.
In the sense that "imo" means "in my opinion, not necessarily in reality".
Clades are just a view on biology. It's not the only one. Otherwise, very few things in biology would exist.
> Well.. eel-like probably more I'd guess.
Still a fish.
The only people who want to see fish cladistically are the ones who don't want fish to be a thing. Fish are obviously a thing, and they are obviously not a clade. It describes function: water, gills, spine.
> eels are not fish
Many disagree.