Re: titanosaurs

[David Marjanovic <david.marjanovic@gmx.at>]

> E.g., if morphological
> cladistic analysis contends that avian flight developed from the ground up,

It doesn't. It can't. What it does, currently, is to say that ground-up is 
most parsimonious. It does so because the groups that have so far been placed 
as close outgroups to birds are interpreted as terrestrial. Well, assuming 
trees-down respectively BCF is the truth, I can easily imagine 2 reasons for 
this discrepancy that have nothing at all to do with cladistics itself.
        One is that the "interpretation as terrestrial" above is wrong. If 
dromaeosaurs are very close to Avebrevicauda, if *Microraptor* is a basal 
dromie, _and_ if *Microraptor* was scansorial, then <pinnng> trees-down has 
become a lot more parsimonious than before. Adding a scansorial 
*Archaeopteryx* even closer to Avebrevicauda, or as the sistergroup to 
dromies + birds, would already make trees-down more parsimonious than 
ground-up. Adding a scansorial *Sinornithosaurus* as a basal dromie, for 
example, would further strengthen this case, as would adding 
*Epidendrosaurus* somewhere basal in this tree, e. g. as the 2nd outgroup to 
birds.
        The other is that taxon sampling suffers from heavy preservational etc. 
bias, obscuring that basal representatives of close outgroups to birds were 
arboreal -- and/or fliers, but then it is necessary that close outgroups to 
the entire flying clade were arboreal, of course. -- Such a bias, e. g. against 
Middle Jurassic taxa, is not in every case an extraordinary assumption, even 
though it is of course not most parsimonious.

> this disagrees with physics

Depends on who you ask :-( . Some say that everything except Ebel's original 
through-the-water scenario disagrees with physics. (Which, just for the 
record, I don't believe for bats, but for them there's only circumstantial 
evidence anyway... same for pterosaurs about which I currently don't have an 
opinion.)