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Re: Dinosaur Genera List update #196



Ralph W. Miller III wrote-

> In the _Nature_ paper, the authors were sufficiently impressed with the
slabs to
> refer to the original fossil as that of a "dromaeosaur."  We are free to
> disagree with this interpretation, of course.

Norell et al. (2002) place it in the Dromaeosauridae based on the elongate
distal caudal prezygopophyses and chevrons, opisthopubic pelvis and enlarged
second pedal ungual.  The first does support this, but the second and third
are primitive for eumaniraptorans.  I agree it's most parsimoniously a
dromaeosaur, but was just pointing out the low character support for this
placement.

> Could it then be a dromaeosaur that is also a basal avialian?  Could
subsequent
> nonvolant dromaeosaurs have lost this feature?  Generally speaking, the
oldest
> deinonychosaurs are the most bird-like, as would be expected in a sister
taxon
> to _Aves_, whether the MRCA be a flying animal similar to _Cryptovolans_
or a
> flightless animal.  Could _Cryptovolans_ and its closest kin have
independently
> acquired advanced flight features?  The fossil record is notoriously
incomplete
> with respect to delicate, hollow skeletons, leaving details of coelurosaur
> phylogeny unresolved.

A dromaeosaur (as I define it- anything closer to Dromaeosaurus than Troodon
or Neornithes, assuming Troodon and Dromaeosaurus are united in a clade that
excludes Neornithes) cannot be a basal avialan.  But yes, I assume a fused
sternum could be lost, though I am unaware of it ever happening in birds.
Of course, fusing/unfusing a sternum sounds easier than convergently
acquiring a dromaeosaur-like tail (though rhamphorynchoids seem to have done
it).  Cryptovolans could be convergently volant, but I doubt it.

> In _Dinosaurs of the Air_, Gregory S. Paul has forwarded his criteria for
> secondary flightlessness in a fossil maniraptoran.  Where do you think his
> character profile is wrong, and what features would you propose as being
more
> appropriate?

I think Paul is basically correct here.  I view all non-volant avepectorans
as secondarily flightless, but don't think ornithomimosaurs, Ornitholestes
or more basal things were.  The idea I was trying to get across before was
that if Cryptovolans were an avialan, all known volant maniraptorans would
be in Avialae, making non-avialan neoflightlessness unnecessary (though
still probable based on morphology, as Paul has argued).

> Aaargh!  I meant _Cryptovolans pauli_.  I apologize for the mix-up.
Apparently,
> _Archaeovolans_ is nothing new, although it's nice to see new photos.  I
would
> like to see intensive independent analysis of _Cryptovolans_ to see what
other
> paleontologists have to say about the specimens.  We have read Gregory S.
Paul's
> support for the interpretation by Czerkas et al. that this looks to be a
genuine
> flying dromaeosaur.  Let's see what other scientists make of it.

I agree that Cryptovolans needs more press.  It would be interesting, if for
no other reason than to see what Feduccia thinks these days.

Mickey Mortimer