[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
AW: Why did *birds* survive K/T?
> In line with the recent work on
> dinosaur respiration, it occurred to me that one reason why
> dinosaurs in general suffered so badly in the K/T event
> might have something to do with the reason why birds now are
> so sensitive to particulates in air (canaries in coalmines);
> because they shared an efficient one-way respiration system
> that extracted the most oxygen it could, but thereby made
> them equally vulnerable to pollutants. That raises the issue
> of why birds themselves would survive an atmosphere rich in
> toxic gases and particulates after the bolide hit. Can
> anyone help me here? Could it have something to do with bird
> distribution (say, being in the Gondwana region as far from
> the impact site as possible)?
Well, that would also facilitate the survival of Gondwanan non-avians.
Perhaps a combination of being in the right place and mobility (enabling them
to seek out patches of remaining habitat).
As far as I can tell, all candidate survivor lineages of theropods were indeed
Gondwanan in distribution at that time. Except perhaps Gaviiformes, which
*probably* were distinct from all other crown lineages back then already but
have a Holarctic (with a capital "A" in fact) distribution today.
There are _Polarornis_ and _Neogaeornis_, but these will have to wait for
restudy (and in the former case, possibly even valid publication) before
anything can be said about a possible Gondwanan origin for Gaviiformes. And
even if these were "proto-loons", the question how they made it from
subantarctic to subarctic waters remains highly puzzling.
In any case, as it seems (from the limited Australian fossil record), at least
part of Gondwana had a higher proportion of avian survivor lineages vs
non-survivor lineages. The enantiornithine diversity of S America still does
not fit the idea of a "simple" geographical bias too well though. In particular
since these were at least partly members of the "ocean-going" clade of enantis
(most enanti lineages/clades are hitherto only known from a single contiguous
landmass; avisaurids or how one would call them are the exception; their
distribution requires ocean-crossing capabilities).
So in conclusion, we see a geographical bias and we see high mobility - but
there is probably at least one other very significant factor. Possibly rapid
maturation (shorter generation times).
Do You Yahoo!?
Sie sind Spam leid? Yahoo! Mail verfügt über einen herausragenden Schutz gegen