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Re: At long last! Turner, Makovicky & Norell on dromaeosaurids
Jason Brougham <firstname.lastname@example.org> wrote:
> Note that it has all kinds of information for those of us who study bird
> origins. It finds no support for the phylogeny of Xu et al., 2011; it moves
> Xiaotingia into the
> Troodontidae, and moves Archaeopteryx back into Avialae.
Having _Xiaotingia_, _Anchiornis_ and _Jinfengopteryx_ at the base of
the Troodontidae means that (unsurprisingly) basal troodontids were
the most "bird-like" troodontids, complete with long arms and a fairly
"modern" plumage. Derived troodontids were better adapted for
cursoriality, and tended to have much shorter arms.
> Furthermore it recovers Epidendrosaurus as a basal avialan (the MOST basal
> one, before Archaeopteryx), and places Epidexipteryx as just outside the
> split between
> Avialae and deinonychosaurs, possibly giving us a glimpse or a model for what
> the ancestral paravian looked like.
Only one additional step is required to put _Epidexipteryx_ in the
Oviraptorosauria; so I doubt if we'd heard the last of where
_Epidexipteryx_ belongs in the Maniraptora tree. _Epidendrosaurus_ is
problematic because of the juvenile nature of the specimen(s).
Another unsettled taxon is _Pedopenna_, which jumps all around the
> It also recovers the most basal dromaeosaur as Mahakala, a short - armed
> form. In this study, when we look at the most basal paravians and their
> closest sister groups,
> we see many forms that do not look extremely flighty (Epidexipteryx,
> Incisivosaurus, Mahakala). This may renew the possibility that the ancestral
> paravian did NOT
> glide or fly, nor even necessarily have long wings. Only an ancestral state
> analysis can assess this question empirically.
_Mahakala_ was certainly not "flighty". But it seems certain that its
short arms were secondary - as in _Caudipteryx_, _Tianyuraptor_, and
derived troodontids. Forelimb length is highly variable among
maniraptorans, but I think there's abundant evidence that a long
forelimb was the primitive condition. for Paraves For me the question
is: Why long forelimbs?
The postcranial skeleton of _Incisivosaurus_ is not known, so the
possibility remains that _Incisivosaurus_ may have had some aerial
locomotory ability. _Incisivosaurus_'s closest relative,
_Protarchaeopteryx_, has very long forelimbs (forelimb feathers are
not preserved - although pennaceous feathers are preserved along the
tail). _Protarchaeopteryx_ might have been some form of parachuter or
glider, in which case this might also be true of _Incisivosaurus_.
Recall that there are biomechamical studies which indicate that true
flapping flight did not arise until fairly late in avialan evolution -
after confuciusornithids. According to Turner &c, the osteological
features involved in bracing the shoulder and re-directing compressive
forces first appear in forms like _Jeholornis_ and _Jixiangornis_, and
after _Archaeopteryx_ and _Sapeornis_. I kinda wonder what these
derived pectoral characters (strut-like coracoid; ball-and-socket
scapula-coracoid; ossified sternum, etc) were used for in proto-birds
that couldn't flap...
> I look forward to a fruitful DML discussion on this pivotal piece.
Be careful what you wish for. ;-)
Brad McFeeters <email@example.com> wrote:
> Strangely for a paper that sets out to review all known dromaeosaurids, there
> is no mention of *Luanchuanraptor henanensis* Lü et al. 2007.
No mention of _Hulsanpes_ either. Still, these are minuscule quibbles
in an excellent body of work.