[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Vegavis gen. nov. - new anseriform in today's Nature



Graydon (oak@uniserve.com) wrote:

<Doesn't show that at all; it shows that the point of common ancestry
between modern ducks and their next closest non-duck relative is back in
the K somewhere.>

  Let's put this another wayss, since the above is both correct, but
misleading, in explaining the situation. Clarke et al. find thyat
*Vegavis* is a member of the CROWN Anseriformes, meaning that it is nested
within in TWO of their analyses the living anseriform birds, aka more
advanced than screamers and anseranatids, but perhaps the sister-group of
anatids (aka, "ducks") and possibly closer to anatids than to anserids
("geese" and "swans"). So, yes, it shows us that *Vegavis* points at the
common ancestor of it and "ducks" were in the Cretaceous, but it also
shows us that the common ancestor of it, geese, swans, ducks, and
screamers, were also in the Cretaceous, so this implies that crown
anseriforms were in the Cretaceous.

<But you're looking at this as though there was no loss of diversity, and
we can be sure there was a substantial one, both through finding
Cretaceous birds that don't have post-K/T descendants, on the one hand,
and through noting that the extant neornithine bird clades represent a
small fraction -- and not the most populous fraction in the Cretaceous --
of the Cretaceous bird diversity.>

  Survival of a crown need have little to do with the diversity of the
clade.

<Motor-gliders, rather than continuous flappers, ill equipped to cope with
a month of global storms.>

  Equibility of flight systems may have caused suffering of ability to
forage in extremes post-cataclysm, such that pterosaurs and
"non-neornithean" birds like enantiornithines would have suffered more
severe losses that, fossiliferously speaking, they were gone at the
Cretaceous--Palaeogene boundary.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
__________________________________ 
Do you Yahoo!? 
Read only the mail you want - Yahoo! Mail SpamGuard. 
http://promotions.yahoo.com/new_mail