[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: BANDS > PADS vs. PALS
> In fact, as Bennett 1996 showed (and Hone and Benton 2008
> confirmed) when you remove hind limb characters
Tim W. wrote:
<<Yes, but why would you want to do this? >>
Bennett (1996) did this. He noted that most of the synapomorphies between
pterosaurs and Scleromochlus resided in the hind limbs, with little else to
promote a relatioship. So he tested the removal of the hind limbs to see where
pterosaurs might end up. I think it was a good test. It demonstrated that the
position of pterosaurs within the Ornithodira was based on flimsy evidence.
It's never a good fit when one is forced to say things like: "Pterosaurs appear
suddenly in the fossil record." Adding fenestrasaurs to the Bennett (1996)
taxon list showed that this previously untested clade had more pterosaur
synapomorphies. That data has never been tested, only dismissed (by Hone and
<<Pterosaurs have legs, so why not
include them in the analysis? Most of the pterosaur bauplan has been
comprehensively modified for powered flight, so (rather than representing
convergence associated with digitigrade locomotion) the hindlimb skeleton may
be best at retaining the ancestral condition. >>
Agreed. That's why you should look very carefully at the ornithodires and try
to see if you can find an elongated fifth toe. If you can't find one among
them, and you won't, it's time to look to other taxa. Also look for digit IV
longer than III. That's the primitive condition in pterosaurs.
<<We see the same trend with birds: the tail, pectoral skeleton (including the
forelimb), and to a lesser extent the skull show profound transformations as
the skeleton became specialized for flight. But the evolution of the hindlimb
was far more conservative over the same period. Besides, the presence of
skeletal pneumaticization and air-sacs in pterosaurs
must count for something. That wasn't known back in 1996. Dinosauromorph
affinities for pterosaurs are looking pretty good right about now. >>
Perhaps it does count for something. The skeleton of Sharovipteryx was hollow.
That's a start. Be interesting to see how far back air sacs go in pterosaurs.
Not sure that's been determined yet. Are they known in Triassic taxa?
<<But what we really need are basal pterosauromorphs. >>
What if you never find them? Good luck in your search.
<<_Scleromochlus_ might fit
the bill; but some of its features are open to interpretation. Nevertheless,
nesting pterosaurs inside Ornithodira is not dependent on the position of
True. However, nesting pterosaurs within the Ornithodira is COMPLETELY
dependent on excluding fenestrasaurs from consideration.
Best to you,