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Re: [dinosaur] Ornithoscelida re-examined, and re-re-examined



David Marjanovic <david.marjanovic@gmx.at> wrote:

> > "Following scrutiny of the character data underpinning our phylogeny1, 
> > Langer et al.2 identify numerous disagreements in terms of character 
> > scoring and suggest changing approximately 2,500 scorings, around 10% of the
> > character data. This extensive re-scoring results in recovery of the 
> > âtraditionalâ topology, although with less resolution and very weak 
> > support; their result is statistically indistinguishable from the 
> > possibility that our topology
> > provides a better explanation of the data. This weak support, despite these 
> > extensive changes, suggests that the âtraditionalâ tree struggles to 
> > account for many character distributions."
>
> Uh, it does. But it also suggests that the Ornithoscelida tree struggles just 
> as much, indeed a little bit _more_, to account for many character 
> distributions. That sentence was a waste of precious space.


I don't envy the authors of both papers - and anyone else seeking to
resolve the origins of the major dinosaur clades (Theropoda -
Ornithischia - Sauropodomorpha).  The validity of Ornithoscelida may
depend on the scoring of a relatively small number of Triassic taxa -
like _Pisanosaurus_ (imperfectly preserved and highly contentious).


Thomas Richard Holtz <tholtz@umd.edu> wrote:

> Criticize the criticisms, and note miscoded cells in Langer et al. Rerunning
> their matrix with some changes, they find  Ithey find herrerasaurs as the
> sister group to Dinosauria, but retain a Sauropodomorpha + (Theropoda +
> Ornithischia) structure. ndependent of other recent analyses, Pisanosaurus
> as a silesaurid. Novel discovery is Daemonosaurus as a basal ornithischian!!


If this position sticks for _Daemonosaurus_ (which I wouldn't bet my
life on), then an argument could be made to resurrect Predentata as
the name for the clade that contains the remaining ornithischians,
which have a predentary (heterodontosaurids, _Eocursor_, genasaurs).
It would also mean that the first ornithischians were carnivores (not
a huge surprise).  Heterodontosaurids might also have retained some
predatory abilities - this is one possible explanation for the
grasping function of the foot inferred for certain heterodontosaurids
(MPEF-PV 3826/?Manidens; Tianyulong), and definitely more plausible
than the alternative hypothesis (arboreal habits).