Re: Adasaurus

[Nick Longrich <nrlongri@midway.uchicago.edu>]

>If understand correctly a partial skeleton of Adasaurus exist. I am not
>aware of all the parts that have been studied but the sickle claw and
>phalanges and distal hindlimb material attributed to it greatly resemble
>Rahonavis. Have the two been systematically compared? I would appreciate if
>one of the theropodists on this list cloud clarify this probable nesting
>within the Archaeopteryx clade being real or false.

More than anything Rahonavis looks like a dromaeosaur in the foot- not just
paravian, not just deinonychosaurian, but dromaeosaurian. Dromaeosaurs are
pretty much alone in having a claw of that magnitude. Well, there's
megaraptor, but then South America may have it's own dromaeosaurs or
dromaeosaur relatives (Unenlagia, e.g. which has those stalked parapophyses
on the dorsals, could be related to them, so maybe  it and Megaraptor are
part of a South American dromaeosauroid radiation. Rank speculation, of
course). I can't think of anything else that has that deeply gynglymous
joint on MT II and III, either.  And the width of MT II distally is pretty
impressive, that's not found in things like troodontids. If people had just
found the foot I doubt any paleontologist would have questioned it as a
dromaeosaur (it's supposed to have a reversed hallux but I think we may be
overestimating the difference between dromaeosaurs and Archaeopteryx in
this respect; the only really big difference I can think of is that it may
lack a proximally massive fourth metatarsal; pictures are too dang teeny to
tell).

>Also has cranial material for Noasaurus been described ever in an accessible
>journal?
>EA

Pretty much everything to Noasaurus is pictured in Dinosauria. There might
be some extra perspectives in the paper by Bonaparte and Powell. I don't
know if the material was actually associated- I think it comes from the
same jumbled bonebed that produced the first crop of Enantiornithes, but
the ungual and cervical exhibit abelisaurian features, the maxilla lacks
the big anterior interior rim to the AOF seen in things above Abelisauria,
and it's all about the right size to go together, so it's probably all one
animal. But scaly theropods aren't really my department.

Oh, yea- Yandangornis has completely fused the sternals together. So that's
another thing maybe arguing that it's a bird. I also think that the animal
might end up doing a pretty good job murdering the idea that oviraptorids
are closer to birds than Archaeopteryx (up to this point I've sort of
flipped a coin on that one). recall that oviraptorosauria+therizinosauria
have a really short tail which(from what we've seen of Caudipteryx) has
only a few pairs of retrices (like a modern bird) instead of the long bony
tail with a massive fan of retrices ( as seen in Archaeopteryx) but
Yandangornis seems to imply that the things that gave rise to pygostylians
had a more primitive tail construction- like Archaeopteryx, but without the
super-long distal caudals; the oviraptorosaurian tail, pygostyle, and
tailplane therefore would be convergent on those of modern birds.
 Of course, oviraptorids might be further from modern birds than
Archaeopteryx- but this in no way leads inevitably to the conclusion that
they are not secondarily flightless...  after all, if it is convergent, why
should the tail converge on the form seen in derived flying birds?