Re: K/T event and amphibians, birds

["Jaime A. Headden" <qilongia@yahoo.com>]

David Marjanovic (david.marjanovic@gmx.at) wrote:

<IMHO Stidham is right in general, but Dyke & Mayr are probably right in this 
special case. I
think that it is much more probable to find the first record of a modern group 
after a mass
extinction like the K-T than before it and basal relatives long after. Who 
knows, it might easily
represent an otherwise unknown group of K birds, maybe some Enantiornithes, 
which convergently
evolved parrot beaks long before the parrots. Parsimony can IMHO mislead when 
there isn't enough
to build it on.>

  Stidham's reply is based on the gross anatomy of the jaw, which locates the 
jaw as a loriid
psittaciform. Dyke and Mayr dissagree not so much on morphological as on 
distributional grounds.
Stidham has replied on this in length on list.
 
<Is there anything new on this subject? Is the oviraptoroid (Sereno for 
Caenagnathoidea + its
stem) character still valid?>

  Oviraptoroidea is not considered a valid taxon. It was named before the ICZN 
third edition; ICZN
2nd ed. dictates that a name based on any family name must be based as its 
eponym on the oldest
family included. That is Caenagnathoidea. This was changed in Sereno, 2000 to 
Caenagnathoidea.
Therefore, unless there is a way to reuse this, it is a subjective junior 
homodefinitional synonym
of Caenagnathoidea. As for the shape of the jaw being indicative of 
caenagnathids, this is true
also of many other birds. The implication of a caenagnathid affinity is 
suggested nearly solely on
the superficial resemblance of the jaw and to its stratigraphic position, 
rather than any real
morphological similarity. In nearly all respects, the jaw appears to be avian 
and shares the most
morphological features with loriid psittaciforms. Therefore, Stadham's 
_tentative_ (in his own
words) referral is logical. As said in his own reply to Dyke and Mayr.

<Ref. 2 is the description of *Caenagnathasia* which I haven't had time to copy 
so far:>

  *Caenagnathasia* does not resemble this jaw in any way. It is much more 
distinct in the nearly
dentigenous nature of the jaw as to be as far from an avian type as can be.

=====
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.

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