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Re: "Elaphrosaurus" gautieri identified as an ......



Mickey Mortimer (Mickey_Mortimer111@msn.com) wrote:

<From the figure, yes, but don't you think Lapparent had some reason to
describe the humerus this way?  Or was it just wishful thinking on his
part? Trying to make "E." gautieri more distinctive than it would be
otherwise?>

  I have no idea what de Lapparent tried to do. Or if he _tried_ anything.
I suspect he drew lines from the cranial and distal ends and estimated a
general measure, and this method may have seemed truly sound and
conservative to him. This is not a reliable means of estimating length of
the humerus. Just looking at some coelurosaur humeri and comparing rations
of length to widths of the proximal and distal epiphyses, it is clear that
the humerus can become hourglass shaped, narrow suddenly above the
epiphysis after some length so that it appears to be broader than not in
the middle, etc. Such a method may adversely effect the length estimate.
That the shaft does not narrow much below the epiphysis is in keeping with
some ceratosaur humeri, and many non-tetanurans. Above this, larger forms
have broader epiphyses, smaller ... well, smaller. Because of his referal
to *Elaphrosaurus*, he may also have tried to conform the humeral
fragments to an *Elaphrosaurus* shape.

<It's possible the proximal tibia is in medial view, but it also resembles
some tibiae in cranial view, such as Avimimus. One would hope Lapparent
knew theropods well enough to orient the tibial ends correctly, he did use
dotted lines to connect it to the distal tibia (indisputably in
cranial/caudal view).>

  I would easily be able to describe what I see. However, if in cranial
view, there are several features that would make the bone unique in all of
archosauromorphs, including a non-cnemial lateral/medial process from
caudal to the cranial surface. This is not parsimonius. What is is that de
Lapparent used a lateral (my confusion for using "medial" above) view and
dotted in the lines to estimate length, instead of a cranial view. I do
not know what was in de Lapparent's head and the only resolution would be
to examine the material first hand. I beleive it is housed at the MNHN in
Paris.

<I don't see a fibular crest, the incisura tibialis would be mostly
hidden, its extensiveness indeterminable.>

  My observation shows that could be an insicura tibialis on the edge of
the tibia, which in lateral view would be quite well apparent. Your
discounting makes me think you're thinking of it as a cranial view when
finding features. A small projection along an edge I discern (I can
illustrate this if need be on my site) apears to be a fibular crest. And
before you try to think I am discounting your theory, I am only presenting
data that to me indicates an alternate interpretation.

<The edge of the ascending process is only certain medially, where it
extends proximolaterally.  It's certainly possible that it was limited
medially, but expanded laterally, like mononykines.>

  I'm talking about extension dorsally. There is no definitive fossa on
the front, and the astragalus is not present. I am not saying it is
lacking, but that it is not clear. This is a bad illustration (not
well-exposed photograph).

<Then explain which ceratosaurs have deep dorsal neural canals (over 40%
of central height) and procoelous caudal centra that are keeled ventrally,
even assuming Lapparent is wrong about the humerus.  And which
Elaphrosaurus-like characters would you be referring to?>

  My observation of *E. gautieri* is restricted to the material in the
plates IV, V, and X. de Lapparent's caudal (pl. X, fig. 5) appears to be
an anterior dorsal with a tall parapophysis on the neurocental suture;
this observation is based on the pneumatic interior structure of the
transverse processes, and their great length along the sides of the neural
arch, a condition that does not occur in other theropods. Ceratosaurs,
however, are noted for the expanded bases of their transverse processes. I
don't know about neural canal height, but a large neural diameter is
present in some other non-coelurosaurs as well, including *Noasaurus,* so
I am not too concerned that this is an exclusive measure of closeness to
birds. Many animals, including small fossil crocodiles (such as the
gracile terrestial ones as in *Pseudohesperisuchus*) and basal
archosauromorphs like pterosaurs and drepanosaurids, have dilated neural
canals.

  As for _my_ characters, I have none. I have not tested the placement of
these two species. de Lapparent used features of the cervical and other
verts to distinguish both of his species, and comparison between them to
differentiate both species. One of these differences in *E. gauthieri* was
that it's caudals were shaped differently, and I think length to height
was used to differentiate both *"E." gautieri,* *"E." inguidensis,* and
*E. bambergi.* It bears well to be skeptical, I guess. Thinking outside
the box, including being willing to turn a bone around and say that it
might be a different view than Bishop de Lapparent preaches. This has
happened before, leading people to, for decades, support a bad contention
as to the view a bone was supported in. There is a tibia (referred to
*Calamosaurus* and *Aristosuchus* as a type, but currently not part of any
species hypodigm as described by Naish (1999, PhD thesis)) which cannot be
discerned front from back, despite illustrations to the contrary. The
distal fossa is present on both sides of the tibia, and this obscures
whether it is a left or right tibia. Caution in identifying things from
plates would be best, especially these plates. Unfortunately, my photocopy
of the paper is limited to *Elaphrosaurus'* 2 new species and three of the
four plates that illustrate its material, this means that I do not have
the plates that illustrate the non-dental or non-vertebral material apart
from what is illustrated in Glut, 1997). 

  De Lapparent (1960) also identified an epiphyseal portion of a bone as
an "anterior caudal vertebra in lateral view" (pl. V, fig, 20) but this
appears in this view to be a distal humerus. Lacking access to any further
id of this specimen, I have no idea what to conclude from this, not having
a 3D interpretation to draw from.

  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.

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