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What Maniraptora is and sin't (was Re: Nitpicky cladistics)



Norm King wrote (quoting Tom Holtz):

> >The word "Maniraptora" BY DEFINITION includes the birds!
>
> It is my sense that birds have not been conclusively shown to be
> descended from deinonychids or any other dinosaur.  So, since we can't
> demonstrate it by the evidence, can we really get around that by DEFINING
> it to be the case? (Yes, I know the prevailing opinion in this group, but
> my question is conceptual.)

Nothing ever can be shown to be *conclusive*, but it can be shown to be so
well supported that it is absurd to think something different without any
compelling evidence to the contrary.  This is the case with birds and
theropods.  The link is os well supported and the evidence to the contrary is
either non-existant, or so vague or ill-interperated that it is clearly
absurd (sorry if I am offending anyone...) to think otherwise *until*
evidence is unearthed that makes a compelling case to the contrary.  With the
theropod-bird link it is VERY doubtful that any evidence to the contrary will
ever show up though (IMHO).

> >If you choose not to use a cladistic taxonomy, then please do NOT use
> >the word "maniraptor".
>
> What happens to maniraptor if you use cladistics to make a case that
> birds are descended from an ornithosuchian?  (Granted, that would require
> some new fossils to be found, but, again, the question is conceptual.)  I
> assume one could define a new cladistics-based category, perhaps the
> "Thecoavia" or even "Ornithornithia," which, BY DEFINITION would include
> birds.

Maniraptora is defined as "all animals closer to _Corvis_ [Birds was actually
used, but I prefer using genera in cladistic definitions] than to
_Ornithomimus_ [again, I believe Ornithomimids or Ornithomimosauria was used
originally]."  So....  If evidence is ever uncovered that _Corvis_ shares a
more recent common ancestor with _Ornithosuchus_ than with _Velociraptor_,
Maniraptora would be:  All birds, All Crurotarsi Archosaurs (including
crocodiles).  Maniraptora is a stem based clade, so it doesn't necisarily
have to include any non-avian dinosaur.  The reason maniraptora is more
associated with dinosaurs is probably because no one calls birds
maniraptorans even though they obviously are *by definition*.  _Velociraptor_
isn't necisarily a maniraptoran because of the way maniraptora was defined,
but _Corvis_ is.

> Perhaps "bird" should be kept separate, being descendants of maniraptors
> (defined differently).

You can't define it differently.  If you want to have a paraphyletic category
for "Oviraptorosaurs, Dromaeosaurs but not birds," you have to make up a new
name for it

> Maniraptora seems to be a legitimate grouping of dinosaurs, whether one
> uses cladistics or not, or whether birds are included or not.  So, any
> non-cladist ought to be able to use it.  It's not a forbidden term for
> them.  They might have to redefine it, but that happens all of the time
> in taxonomy.  No reason why it can't happen to terms established by
> cladists.

But, as I said before, Maniraptora is not defined as having ANY members that
are non-avian dinosaurs.  Maniraptora is: everything closer to _Corvis_ than
_Ornithomimus_; nothing more, nothing less, and CERTAINLY NOT a paraphyletic
group containing ONLY Dromaeosaurs and Oviraptors.

Peter Buchholz
gpb6845@msu.oscs.montana.edu

"I just looked at them."