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Re: Semilunate Carpal: Application of Description



Ken Kinman wrote-

>      I'm wondering how reflective these codings are for groups in general,
> particularly for the second character (unfused vs. fused distal carpals I
> and II) in groups like ornithomimes.
>       Also I am wondering if, once fused, they would likely become
unfused.
> It seems more likely that unfused would be primitive, and that fusion
> occurred several times among coelurosaurs (rather than having reversals
from
> fused to unfused).

Sure, why not become unfused?  If fusion was only capable of evolving and
not reversing, you'd have big problems.  For example, Madsen reports 14 of
18 Allosaurus specimens have fused carpals, regardless of maturity.
Megapnosaurus (cringe) is similar in this regard.  Then you'd have to have
the various basal coelurosaurs (Sinosauropteryx, tyrannosaurids?, Coelurus?,
Scipionyx?, ornithomimosaurs) develop fused carpi independantly (though you
could get away with putting Coelurus and Scipionyx in a separate lineage to
drop the steps by one, as basal coelurosaur phylogeny is virtually unknown).
It would be _massively_ unparsimonious.

Mickey Mortimer