If it loses that trait, it is no longer considered a synapomorphy now is it? Logical fallacy.
Now perhaps you can go back and read what I said.
Under cladistics, the only characteristic is the shared ancestor. Any other trait is irrelevant.
That is because by definition, any descendant must be part of the same clade, regardless of any other trait.
That means the clade would then need some other defining trait.
Also, you just contradicted yourself entirely. You admit I am promoting phylogenetics. Yet then you say under evolutionary taxonomy, birds aren't dinosaurs. Even though you previously and explicitly said you reject evolutionary taxonomy. Make up your mind.
Again, go back and read what I said.
I admitted I made a mistake with the terminology.
I was arguing against cladistics, which is what you are promoting, not evolutionary taxonomy as I thought. Evolutionary taxonomy allows paraphyletic groups, i.e. a descendent can lose the defining trait and thus no longer be part of the group. Cladistics does not, i.e. a descendent can lose the defining trait, but must still be part of the group.
You keep saying eukaryotes are all descendents of prokaryotes. They share a common ancestor. There is a huge difference.
No, there isn't a huge difference. You are just taking my statement and making it more general. There is no disagreement between that statement and my one.
The common ancestor was a prokaryote.
All clades which include all prokaryotes includes the eukaryotes.
Just like all clades which include all fish includes land animals like birds and humans.
Remember, birds are dinosaurs.
Remember, only if birds
are fish and birds
are prokaryotes.
Birds are not fish since fish is not a taxonomic group in systemic biology. So Try again.
If you want to play that game, neither are dinosaurs.
The group you are thinking of is known as Dinosauria.
So your argument should thus be birds are members of the group Dinosauria.
Or we could just use Pisces, an old taxonomic group pretty much meaning fish.
And if you want to say that members of dinosauria are dinosaurs, then members of Osteichthyes, which under cladistics needs to include humans, would be bony fish.
So instead of humans being fish, they would need to be bony fish.
If people want to use a new system with significantly different meaning, they shouldn't be using the old words.
If we want to group things without ANY consideration or the most recent common ancestor we can have terrible classification:
Ex: All winged animals are a family! Should a butterfly be considered closely to related to a penguin?
We can even make arbitrary groups:
Ex: All green organisms are a family! Plants are just like frogs! Great!
So you throw all reason out the window and instead try and focus on a single trait.
Guess what? That is no worse than saying:
"Well they evolved from X, so they must be X".