RE: Koreanosaurus, new burrowing ornithopod [Meta]

[Tim Williams <tijawi@yahoo.com>]

Anthony Docimo <keenir@hotmail.com> wrote:


> > Unless _Koreanosaurus_ is included in a phylogenetic
> analysis, then any discussion of its relationships is just
> hand-waving.
>  
>  on the contrary.  if that were true, then nobody here
> would be calling it an ornithopod.


I'm only calling it an ornithopod because the paper calls it an ornithopod.  
The paper calls it an ornithopod because they list certain characters that 
_Koreanosaurus_ has in common with ornithopods.  But the paper specifically 
calls _Koreanosaurus_ a 'basal ornithopod', which puts _Koreanosaurus_ 
uncomfortably close to Marginocephalia, as well as uncomfortably close to 
non-ornithopod genasaurs like _Othnielosaurus_ (which lies) outside the 
Ornithopoda-Marginocephalia clade).  


Personally, if the authors are going to explicitly link _Koreanosaurus_ to 
_Orodromeus_ or _Oryctodromeus_ in a phylogenetic sense, then I would really 
prefer to see this hypothesis tested.  


> (we'd all be terrified of repeating the mistake of confusing a dinosaur
>  with a turtle   (ie Therizinisaurs))


Sorry, you lost me here.  I know _Therizinosaurus_ was originally misidentified 
as a turtle.  Phylogenetic analyses have recovered _Therizinosaurus_ within the 
Theropoda, close to _Segnosaurus_, _Alxasaurus_, etc.  That would seem to bear 
out my point regarding the necessity of using phylogenetic analyses to 
determine relationships.


>  we know it's a dinosaur, we know it's an ornithopod, we
> know it isn't a maniraptor or pterosaur.


No, we don't know it's an ornithopod (see above).  But even if _Koreanosaurus_ 
is an ornithopod, that doesn't tell us very much.  Is it most closely related 
to _Orodromeus_ and _Oryctodromeus_?  This has repercussions for the question 
of whether fossorial adaptations evolved only once in Ornithischia.

 
>  so why can we talk about what it may be similar to, but
> the discoverers/describers can't?


Well, the describers provide a cladogram that shows _Koreanosaurus_ as sister 
taxon to _Orodromeus_ within the Ornithopoda.  I'm u
n into a cladogram unless the relationships of the taxon have actually been 
tested.  Yeah, _Koreanosaurus_ is probably a true ornithopod, and it might 
indeed be most closely related to _Orodromeus_ and/or _Oryctodromeus_.  But 
only taxa that have been plugged into the matrix should be shown in a 
cladogram.  Otherwise it's misleading.  



Cheers

Tim