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re: kellner's ankle abstract



  I will reference a few things said at the end of this email, before I
dig into the rest. But I would like to comment on the argument suggesting
that *Lagerpeton* has a rather "pterosaur-like" pes, given the comments
earlier in the referenced post. 1) *Lagerpeton* is the most basal
dinosauromorph, and in fact so far is the only non-dinosauriform
dinosauromorph, so what other taxa have or not is irrelevant, since both
*Marasuchus,* *Pseudolagosuchus,* and *Silesaurus* have been positioned
right at the dinosaur/non-dinosaurian archosaurian boundary, as it were,
if not over it, which has never been the case for *Lagerpeton.* 2) All
species have autapomorphies, and even when pterosaurs are considered
closer to dinosaurs than are crocs, these features of the pes remain
stable as autapomorphies for *Lagerpeton,* while the cylindrical
astragalus, small calcaneum, expanded distal tibia and fibula contacting
and forming a calcaneum/astragalus concavity structure not found in crocs
or "basal protorosaurs" (in ANYONE'S scheme, given the elongation of these
elements with a separation of the tibia and fibula by rod-like proximal
tarsals), imply a closer relationship with dinosaurs than with crocs, or
other archosauromorphans.

  Dave Peters (davidrpeters@earthlink.net) wrote:

<DP: If you assume an Archosaurian ancestry, which is not the case...>

  This is a rather bold statment, given that there are competing
hypotheses, without any sort of "settled" case. So, one should put a
qualifier in one's statement stating in such definite terms. Like, "if,
and only if Peters 2000 is true...." and so forth.

<Once again, Kellner knew of the protorosaur paper. He refereed it.
Puzzling why he chose to put on blinders here.>

  Ask him why, don't assume a motive ("...put on blinders..."). 

<Like others, apparently Kellner is clinging to what he?s been taught and
what he teaches to others. Still, this is only one mistake. Kellner?s body
of work has many stars. Mistakes are allowed. BTW: Anytime someone has
reason to believe that pterosaurs are archosaurs, send me the evidence. If
it?s valid, I?ll hand carry a six-pack of your favorite beverage to you
anywhere in the world.>

  A cladistic analysis of dinosaurs with pterosaurs had not been performed
until nearly the 90's, so it is likely the time between then and now is
not long enough to produce any sort of "dogmatic" rule, especially with
the increasing intensity with which many cladistic analyses are looked at
in. This includes Peters 2000, and because it's so "outre" with regards to
other phylogenies, it is given a good deal of scrutiny. Notice that the
scientific community isn't jumping up and holding each new analysis of
hominine phylogeny as "the Holy Grail," as I think giant, bloodthirsty
bunnies do a better job at that. Similarly, anything of such a disparate,
critical nature is not touted as "the honest truth" until supported by
other work. Theropod phylogeny remains somewhat in flux at certain
critical points, but perhaps not so much as Holtz's "Rule of T" (wherein
taxa beginning with "T" tend to be destabilizing in coelurosaur phylogeny:
Therizinosauroidea, Tyrannosauroidea, and Troodontidae, and this remains
the case with more or less similar results through the last half-decade),
and basal theropods, dinosaur origins, origin and diversification of the
Ornithischia, as well as the Sauropoda, remain contentious because of the
lack of agreeing phylogenies.

  Is it possible that the reason one might want to consider their own
phylogeny "the truth" is because it is their own? This is what Tim was
referring to as a "pet theory," since you want to pet it, love it, take
care of it, like a pet, and make it do what you want. Beautiful, perfect
things tend to be the veneer which is spread over peoples' worries, such
as "gross" stone work, skeletal frames, cold metal and steel, in order to
"hide" or "create" something. And like the flawed beginning of a Fabergé
egg, eventually the end product becomes so involving and involved and
detailed that any imperfection, however major, will be overlooked as a
"quirk." Some elaborate on quirks, a cladistic "spandrel," by developing
theories around unusual occurences, and *Lagerpeton* is no exception.

  Kellner's work exemplifies a similar condition: rather than look at
basal pterosaurs, his look was at several advanced ones. The basal ones
tend to have less detailed ankles, for the most part coming to us from the
Solnhofen, which isn't that too detailed in bone anatomy as it is in
soft-tissue preservation, as in most [konversat]lagerstätten, but just
looking at *Pterodactylus* I can tell you that the large astragalus dwarfs
the tiny calcaneum, and while disarticulated, a large cylindrical object
is present in the tarsus of the second *Peteinosaurus,* mimicked in
*Preondactylus,* with similar but not identical structure in
*Rhamphorhynchus.* No object data, but my sources are the lovely photos
from Wellnhofer's book, which are freely available, and give one an idea
to expand research into. Not looking at basal taxa gives one an
interesting picture, but one needs to look at basal forms when known to
elaborate on the idea. So, Kellner's example may or may not be challenged
by further data. There is no need to question the man, just the work, and
the details therein (like a cladistic analysis NOT based on unverified
tracings).

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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