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RE: Dromaeosaurid tails like rhamphorhynchid tails from flight use



Unenlagiines don't have elongated prezygapophyses and chevrons, based on 
Rahonavis and Buitreraptor.  Also you no doubt meant Anchiornis may be a basal 
troodontid, not Tianyuraptor.

Mickey Mortimer

----------------------------------------
> Date: Thu, 17 Jan 2013 08:27:20 -0700
> From: qi_leong@hotmail.com
> To: augustoharo@gmail.com; Dinosaur.Mailing.List@listproc.usc.edu
> Subject: RE: Dromaeosaurid tails like rhamphorhynchid tails from flight use
>
>
>   The outgroups (*Troodontidae*, *Archaeopteryx lithographica*) lack 
> elongation of the prezygapophyses, chevrons, or of the extent seen in 
> dromaeosaurids proper of the median caudal vertebrae. Basal microraptorians 
> have these features, as it seems do "unenlagiids," as of course 
> *Dromaeosauridae* sensu stricto (*Eudromaeosauria*). Depending on where 
> *Mahakala omnogovae*, *Anchiornis huxleyi*, and *Tianyuraptor ostromi* fall 
> (with recent analyses indicating variability, though the latter as a basal 
> "troodontid" [sensu lato]), this implies that the caudal anatomy is 
> diagnostic within the clade (*Dromaeosaurus albertensis* but not *Troodon 
> formosus* or *Vultur gryphus*/*Passer domesticus*), but not outside of it. If 
> so, then a fully arboreal and/or volant basal dromaeosaurid is not optimized 
> as _the_ ancestral form; and instead, *Anchiornis huxleyi* and *Archaeopteryx 
> lithographica* indicate a related lineage (again, without the tail features 
> remarked here) which either attain or retain volancy of some form.
>
> Cheers,
>
> Jaime A. Headden
> The Bite Stuff (site v2)
> http://qilong.wordpress.com/
>
> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>
>
> "Ever since man first left his cave and met a stranger with a
> different language and a new way of looking at things, the human race
> has had a dream: to kill him, so we don't have to learn his language or
> his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
> Backs)
>
>
> ----------------------------------------
> > Date: Thu, 17 Jan 2013 12:15:29 -0300
> > From: augus
> > To: martyniuk@gmail.com
> > CC: tijawi@gmail.com; dinosaur@usc.edu
> > Subject: Re: Dromaeosaurid tails like rhamphorhynchid tails from flight use
> >
> > I would rather think character optimization should indicate whether or
> > not the features of Mahakala are primitive or derived for
> > dromaeosaurs, not time after divergence, at least if we follow
> > parsimony.
> >
> > Cheers,
> > Augusto.
> >
> > 2013/1/17 Matthew Martyniuk <martyniuk@gmail.com>:
> > > I'd be careful assigning such significance to Mahakala. It is at least
> > > 75 Ma removed from the common ancestor of all dromaeosaurs. So while
> > > Mahakala may be among the most basal dromaeosaurs, that doesn't
> > > necessarily mean it's the most primitive. Monotremes are the most
> > > basal living mammals, but that doesn't mean the ancestral mammal was
> > > platypus-like. It's always possible that such odd (for a dromaeosaur)
> > > features as very small forelimbs and un-stiffened tails in Mahakala
> > > were due to some novel ecological niche (burrowing?).
> > >
> > > Matt
> > >
> > > On Thu, Jan 17, 2013 at 1:12 AM, Tim Williams <tijawi@gmail.com> wrote:
> > >> Ben Creisler <bcreisler@gmail.com> wrote:
> > >>
> > >>> W. Scott Persons IV & Philip J. Currie (2012)
> > >>> Dragon Tails: Convergent Caudal Morphology in Winged Archosaurs
> > >>> Acta Geologica Sinica - English Edition 86 (6): 1402–1412
> > >>> DOI: 10.1111/1755-6724.12009
> > >>> http://onlinelibrary.wiley.com/doi/10.1111/1755-6724.12009/abstract
> > >>
> > >>
> > >>
> > >> The paper seems to be saying that the chevron and zygapophyeal caudal
> > >> rods of dromaeosaurids evolved in an aerial/arboreal context (as in
> > >> rhamphorhynchoids). In other words, the specialized stiffened tail of
> > >> dromaeosaurids evolved "on the wing" to assist in gliding or flying.
> > >> Therefore, the highly specialized tail of large, and presumably fully
> > >> terrestrial dromaeosaurids (such as _Deinonychus_ and _Velociraptor_)
> > >> would be a relict of an aerial/arboreal ancestry (represen
al
> > >> dromaeosaurids such as _Microraptor_)... according to this hypothesis.
> > >>
> > >>
> > >> I'm not convinced. Little _Mahakala_, which comes up as the most
> > >> basal dromaeosaurid, lacks the elongate prezygapophyses and chevrons
> > >> present in more derived dromaeosaurids; but it nevertheless has an
> > >> underdeveloped fourth trochanter. So unless _Mahakala_'s caudal
> > >> features are a reversal (like the short forelimbs), then the presence
> > >> of rod-like prezygapophyses and chevrons in more derived
> > >> dromaeosaurids is not necessarily correlated with the proposed
> > >> reduction in femoral retraction (i.e., a more bird-like locomotor
> > >> style).
> > >>
> > >>
> > >> Both "Groucho running" and caudal rods are regarded by this study as
> > >> indicators of aerial behavior (or descended from ancestors that
> > >> exhibited aerial behavior). I'm still extremely skeptical that
> > >> deinonychosaurs had a bent-legged locomotor style ("Groucho running").
> > >> I'm still extremely skeptical that deinonychosaurs had a bent-legged
> > >> locomotor style ("Groucho running"). And as for the caudal rods:
> > >> _Deinonychus_, _Velociraptor_ and _Achillobator_ had these specialized
> > >> caudal rods, even though they were not likely to have been aerial
> > >> gliders (or fliers!) Presumably these highly specialized rods had a
> > >> purpose in these large, derived dromaeosaurids that had nothing to do
> > >> with aerial behavior. If so, maybe the original purpose for these
> > >> caudal rods also had nothing to do with aerial behavior.
> > >>
> > >>
> > >> The authors aver: "A thin light-weight tail with reduced caudofemoral
> > >> musculature that preferentially retains lateral flexibility while
> > >> increasing dorsoventral rigidity is well suited for a flying or
> > >> gliding animal." I don't doubt that this is true. But that doesn't
> > >> mean such a tail couldn't be used for other behaviors. The
> > >> biomechanical pressures might have been similar between the tails of
> > >> dromae
ssures
> > >> may have been quite different. Ostrom's hypothesis that _Deinonychus_
> > >> attacked prey much larger than itself has been criticized by some
> > >> (e.g., Darren Naish), but I'm more supportive. Perhaps the
> > >> specialized tail of dromaeosaurids was associated with predation -
> > >> more in line with what Ostrom proposed in 1969 for the tail of
> > >> _Deinonychus_.
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >> Cheers
> > >>
> > >> Tim
>