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Re: Cladistics (was Sci. Am. - present)






>We have had a rather sparse response to my request for known mesozoic =
>uncinants - there can't be many - and of course any birds or bird-like 
=
>dinos that don't have them.  I'm sure many apart from myself would be =
>interested in our most up-to-date assessment.

>John V Jackson    jjackson@interalpha.co.uk

>(Wannabeasaurus   beecee-effia - & proud of it!)


     It's  _uncinate_.

 Anyway, back to uncinates. In non-avian dinosaurs as far as I can tell 
they are present in dromaeosaurs for certain due to the vast Gobi 
fossils found. 
 
    Uncinates are absent in osseous form in Archaeopteryx, 
Confuciusornis, and enantiornithines. Some have speculated that they may 
have been cartilageous; possible, but unlikely. 

    All ornithurine birds have uncinates, though there are derived 
exceptions. They are found in modern form in Liaoningornis, the earliest 
ornithurine bird. Chaoyangia has them. Ambiortus has them. 
Hesperorniformes have them. A possible basal or near-ornthurine lacks 
them, Patagopteryx. And neorntihines all have them. 

  
     Putative uncinates:

 In the numerous oviraptorid specimens there are always prong-like 
processes around the ribs that may be uncinates. 
 
 Note: the uncinates in dromaeosaurs seem to be seperate ossifications 
which makes them questionable. 

 The basal stegosaur, Huayangosaurus, as reconstructed in Dong 1990; 
Dinosaur Systematics, has strange processes hinging on the ribs, but 
don't overlap. 

 Out of the Dinosauria and into Crocodylomorpha. Gavials have 
uncinate-like processes and so do many other crocs. These are 
cartilageous and may not be homologous to bird uncinates.

 This imformative?


 WMattTroutman

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