[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Greg Paul on new description of Spinosaurus



The authors of the original study have reliably and timely responded
to online criticisms one many of these topics and have attempted, at
the least, to cover the probability of the wholeness of the specimen
in the paper. The commentary noted above resolves NOTHING that cannot
be discounted by original reference to the paper; it offers no new
methodor information to determine the facts asserted, or to refute
those of Ibrahim et al. Furthermore, the authors have cautioned the
degree of response due them on account of a longer, more complete
monograph in preparation. While some criticisms about the paper may be
valid, those that deal with the specimen itself cannot be qualified
without access to the data at hand, leaving us with little recourse to
wait. Thus commentaries like the one above serve little purpose than
to stoke the fires of contention. Let the authors publish the data,
first.

On Tue, Dec 2, 2014 at 2:51 PM, Ben Creisler <bcreisler@gmail.com> wrote:
> >From Greg Paul:
>
> ---------- Forwarded message ----------
> From:  <GSP1954@aol.com>
> Date: Tue, Dec 2, 2014 at 2:17 PM
> Subject: Posting
> To: bcreisler@gmail.com
>
>
> Please post the below, thanks,
>
> Greg
>
> http://comments.sciencemag.org/content/10.1126/science.1258750,
>
>
> Ibrahim et al. have taken an assortment of incomplete spinosaur remains
> found
>
> over an enormous territory of North Africa spanning 3000 km, found in
>
> sediments whose exact temporal correspondence is not certain, and presumed
>
> that they represent one genus and species. This despite the specimens being
>
> limited in overlapping comparative material, being of different ontogenetic
>
> stages, and there being some uncertainty concerning the individuality of
> some
>
> specimens -- a large gap in the vertebrae of juvenile/s FSAC-KK 11888
> between
>
> the mid dorsals and sacrals makes the conclusion it is one individual a
>
> matter of opinion. The unusual length of the dorsals relative to the pelvic
>
> sacral/pelvic/hindlimb elements in 11888 is suspicious, and should not be
>
> presumed real unless it is present in a more complete and articulated
>
> specimen, preferably adult. An attempt by this experienced paleoillustrator
>
> to use the array of specimens to produce a reliably proportioned composite
>
> technical skeleton of Spinosaurus aegypticus was abandoned due to these and
>
> other issues – it is my experience that composite skeletons of novel taxa
>
> constructed under these circumstances later often prove substantially errant
>
> when more complete specimens are obtained. The actual skeletal proportions
> of
>
> Spinosaurus therefore remain uncertain, and the extreme shortness of the
>
> hindlimbs restored by Ibrahim et al. is questionable, although the
>
> possibility that the genus had exceptionally abbreviated legs cannot be
> ruled
>
> out.
>
> Even more open to challenge is the near equality of the length of the arms
>
> relative to the legs, and the idea that the theropodian arms were used in
>
> locomotion. Attempts to calculate the absolute center of mass of extinct
>
> dinosaurs even when the specimen is a complete individual is always
>
> debatable, and doing so with a problematically proportioned composite based
>
> on so many individuals of differing ages from so many places risks producing
>
> misleading results.
>
>     Also doubtful is the designation of FSAC-KK 11888 as the neotype of S.
>
> aegypticus. Minimal overlapping material, differing ontogenetic stages,
>
> possible time separation, and the 3000 km separation make it very possible
>
> that 11888 and the destroyed holotype represent different taxa. The
>
> possibility that 11888 is more than one individual is another difficulty in
>
> this regard.
>
>         Ibrahim et al. appear to have over interpreted the available
> fossils.</HTML>



-- 
Jaime A. Headden
The Bite Stuff: http://qilong.wordpress.com/


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