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Re: Mesozoic roots of parrots and passerine birds



2011/8/27 Jaime Headden <qi_leong@hotmail.com>:
>
>   ...Dyke and Mayr have argued, does not resemble that of Paleogene or 
> Neogene psittaciform fossils.

Of course not doubting of the huge knowledge both Mayr and Dyke have
regarding paleontology of modern birds, but it seems to me a weak
argument to claim that a cretaceous parrot should be more similar to
Paleogene birds than to Recent ones. For it is so common in the fossil
record that generally more plesiomorphic (and thus basal) specimens
appear later in time than early generally more apomorphic ones.

>I comment futher here: 
>http://qilong.wordpress.com/2011/03/02/a-cretaceous-parrot/ . It may still be 
>avian, however, and I specifically do not take this argument because of a 
>limited level of comparison. It is, in any case, psittaco-morphic (having the 
>shape of a parrot) but this is a generalization based on the rounded of the 
>rostral margin, fusion, and the shape of neurovascular canals both within and 
>upon the symphysis.

Thanks for the further clarification and elaboration. But although
Dyke and Mayr (1999) stated that the vascular K-like mark was present
in other birds, I was not able to find in their comment, or in your
review, evidence that non-avialan theropods present that vascular
trait stated by Stidham. So, in my opinion, although these are few
features (few arguments) on the basis of which to allocate the
specimen, I think that Stidham's still seems to be the most
parsimonious inference on the basis of the analyzed anatomical
features of the specimen, unless there is a further study I do not
know nothing of stating otherwise.

Of course, a phylogenetic analysis including the material should be
better than this opinion, for there is the possibility that because of
being so incomplete and thus full of missing data, the material jumps
between several alternative positions, weakening the allocation by
Stidham.

The only argument it seems to me there currently is against Stidham's
systematic allocation is a stratigraphic one, and in my opinion these
arguments are weak, as systematics are based on anatomy and not
bichrons.

Of course one may still be wrong if following Stidham's systematic
judgement, as in the case of the Revueltosaurus teeth, but it may be
said that at the moment Revueltosaurus' teeth were first recovered,
considering them ornithischians was the best guess possible, if the
teeth shared more apomorphies with then known ornithischians instead
of then known crurotarsans.

Cheers,
Augusto
>
> Cheers,
>
>  Jaime A. Headden
>  The Bite Stuff (site v2)
>  http://qilong.wordpress.com/
>
> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>
>
> "Ever since man first left his cave and met a stranger with a
> different language and a new way of looking at things, the human race
> has had a dream: to kill him, so we don't have to learn his language or
> his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
> Backs)
>
>
> ----------------------------------------
>> Date: Fri, 26 Aug 2011 20:05:17 -0300
>> From: augustoharo@gmail.com
>> To: dinosaur@usc.edu
>> Subject: Re: Mesozoic roots of parrots and passerine birds
>>
>> Changing a little the axis of the discussion, was it proved that
>> pretended Cretaceous parrot (Stydham, 1998, in Nature) was actually
>> not a parrot? Dyke and Mayr's 1999 reponse stated it may be a
>> non-avian theropod, but I was not able to find refutation (it may be
>> said that because of being Cretaceous, the burden of proof is on
>> proving it is a parrot, but the best test would consist in including
>> the specimen in a data matrix of maniraptorans).
>>
>> Cheers,
>>
>> Augusto
>