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



Jaime Headden wrote-

> 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.

The shaft does not decrease in width any differently than Mononykus proximal
to the epiphyses.  I fail to understand how restoring the humerus as short
and stout would have "conformed to an Elaphrosaurus shape", when the latter
has very slender humeri.

>   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.

Compare the tibia of Avimimus in posterior view.  The only difference is
"E." gautieri has a larger medial condyle and a posterior groove (which is
found in most theropods, Avimimus being an exception).  Part of the reason
the medial condyle could look so large is that part may be the cnemial crest
extending laterally past it.  So the tibia hardly has "several features that
would make the bone unique in all of archosauromorphs".

>   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.

I think your incisura tibialis is the posterior groove.  If you're speaking
of the ridge on the right edge of your cnemial crest when referring to a
fibular crest, it is positioned much to proximally, even for a ceratosaur.

>   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).

Can't be used to counter an alvarezsaurid interpretation then, can it?

> <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.

The reason figure 5 of plate X appears to be a dorsal is that it IS A
DORSAL.  Note Lapparent labeled it as such "Elaphrosaurus gautieri nov. sp.
Vertebre dorsale".  The transverse processes don't appear to be preserved.
I'd be VERY interested to hear how you know Noasaurus has "large neural
diameter", when no dorsal neural arches are known and the only preserved
dorsal centrum is undescribed.  Even the cervical neural canal height is
undescribed and not measurable in the figure.  So now that Noasaurus is
discounted, which "other non-coelurosaurs" are you referring to?
Referencing non-dinosaurian taxa is useless unless you want to propose "E."
gautieri is non-dinosaurian.
I notice you could not find ceratosaurs with procoelous ventrally keeled
caudal centra.  Look at plate V figure 5 for a caudal centrum of "E."
gautieri.

>   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.*

The only comparable parts of "E." gautieri and "E." iguidiensis are the
distal caudal centra and proximal tibiae.  The former of "E." gautieri are
procoelous, those of "E." iguidiensis are ampicoelous.  The tibia of "E."
iguidensis is nether described, nor illustrated.  He referred "E."
iguidiensis to Elaphrosaurus based on similar distal caudal length/height
proportions, and did not justify referring "E." gautieri to Elaphrosaurus,
though he said the humerus was similar.  The only reason he assigned "E."
gautieri to a new species was because it was smaller than E. bambergi and
had undescribed "accentuated differences".

>   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.

He identifies that as a proximal caudal's transverse process of
"Rebbachisaurus" tamesnensis- "apophyse laterale de vertebre caudale
anterieure".  The supposed shaft in your interpretation would be much too
narrow for a hunerus.  Compare it to the transverse process of
Haplocanthosaurus' proximal caudal for instance (revised Dinosauria, pg.
363).  They are quite similar.

Mickey Mortimer