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

RE: titanosaurs



 
Dinogeorge wrote:

> For example, why is "neural spines bifid" a character but "dorsal 1 
> neural spine bifid," "dorsal 2 neural spine  bifid," "dorsal 3 neural 
> spine bifid," and so on, are not (yet, anyway)?

Of course, there is an arbitrary and subjective component to any character
codings.  For example, the morphology of proximal, middle, and distal
caudals may be assessed as three different characters in sauropods.  Thus
the caudal series is split up into groups of vertebrae, based upon their
position in the series.  Nor I am I dismissing out of hand the idea that
every single vertebra in a series qualifies as a discrete character.  But
setting aside the likelihood that such characters are developmentally and/or
functionally linked, I don't see how it gets us closer to recovering a more
"accurate" or "real" phylogeny.  After all, what are you testing it against?

As I said before, does it make sense to regard every wing feather of
_Archaeopteryx_ as a separate character?  Or every tooth in a hadrosaur's
jaw as a separate character?  And to return to the original question: Does
treating each and every vertebra of _Opisthocoelicaudia_ as a separate
character remove it from the Titanosauria?  A proximal-medial series of
opisthocoelous caudals appears to be unique to _Opisthocoelicaudia_ anyway,
so how does it disprove titanosaur affinities?  It's not as though there are
non-titanosaurs out there that are known to have this feature (or set of
features).   

> Our best chance at doing something approaching accurate/real taxonomy is
> to consider character suites (whatever they might be), biostratigraphy, 
> biogeography, and anything else we can think of, and see how they stack
> up against one another. 

A reasonable suggestion.  However, I wasn't aware that "biostratigraphy, 
biogeography, and anything else we can think of" were at odds with putting
_Opisthocoelicaudia_ in the Titanosauria.



Tim