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Re: [Spinosaur Variation]



"Jaime A. Headden" <qilongia@yahoo.com> wrote:
Meanwhile, while theropods around the Jurassic and
> earliest Cretaceous were playing with sails, we have
> some unsual cranial variation within spinosaurs, and
> this brings me to my original purpose for this post.
> 
>   *Spinosaurus'* lower jaw suggests the animal had a
> short, relatively stout cranium. It was certainly
> deeper relatively than other spinosaurs known. The
> length of the dentary, at 2ft, suggests that skull was
> little more than 3ft long in total, perhaps a meter at
> most, and this was shorter than Bary's estimated skull
> length, especially as an adult (around 3.5ft, as
> reconstructed using Sucho as a guide).

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So, we assume short and robust in Spino like we would in Nile crocs (short
stout and to the point), or are we making a return to the original view of a
bulldog snout? 

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>   *Baryonyx* and *Suchomimus* are considerably alike,
> and have the very long, shallow jaws that can be used
> to compare Spino's in approximating a complete
> mandibular reconstruction, and from that, building a
> cranium to fit, using (again) Bary and Sucho as
> guides. These two were the most croc-like of the
> bunch, with the sigmoid curvature of the upper jaw
> being quite swung in front.
> 
>   *Cristatusaurus* (Taquet and Russell, 1998) had a
> jaw nearly identical to *Baryonyx*, as Sereno et al.
> 1998 suggested but did not go into detail about, but
> there is a significant difference between the two, in
> that the "adult" specimen of the premaxilla [holotype]
> has a midline ridge (not a crest) that suggests the
> nose had a very long nasal crest. Similar to
> *Angaturama*, but again, not a crest, it was too
> broad. This suggests that Cristatu is at least a new
> species, rather than being a nomen dubium. It may be a
> subjective junior synonym of *Baryonyx,* but *C.
> lapparenti* is distinctive enough (including fused
> premaxillary suture at a size comparable to Bary's
> type) to become another species of Bary (*B.
> lapparenti*?) or even Sucho (which would susume Sereno
> et al. into Cristatu, and *S. tenerensis* is the
> subjective).
> 
>   _Anyway_, Taquet, 1984, and Taquet and Russell,
> 1998, described a set of jaws (upper and lower) as the
> latter paper refered them to *Spinosaurus* (*S.
> moroccanus*), but failed to mark a distinction in
> their size. The premaxillae are almost a foot long,
> larger than Sucho by about 200%, and the whole upper
> jaw fragment measures nearly two feet, with a
> maxillary anterior process; but the fragment's shape
> and very shallow depth shows that the external naris
> would either have been very slit like and long, or
> been posterior to the fragment, adding about a foot
> more, and ... well, to cut it short, I estimate the
> skull of this animal (again, using the above
> comparisons and guides) to be about 2.2m (~7ft)!

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2.2 meters, whoa!!! I guess that makes *Cristatusaurus* the most gharial like
spinosaur yet. Was this one found near an area that would have contained fast
flowing water (river, delta)? Any teeth to go with the skull?

********************************************8
 
>   *Irritator* and *Angaturama* are probably the same
> species, though no comparative fossils are known, but
> it is unlikely that they are the same specimen as
> previously suggested on the list. Nonetheless,
> *Irritator*'s skull appears to have been crushed
> posteriorly, making the rear of the skull very
> fragmentary, even the quadratojugal is missing, and
> the quadrate is anteriorly displaced, being upswept
> into the orbital space. Additionally, the nasals have
> been dorsally eroded or broken off, and there's a
> process posterior to the orbit and crest that is
> probably the paroccipital process or squamosal, and
> this suggests the skull is much longer than Martill et
> al. illustrated. The lower jaw also appears to have
> been at least partially ventrally displaced. And
> that's my personal observation. Total, the skull, if
> sticking *Angaturama*'s snout on front, would make the
> skull around 3ft long. Meanwhile, the crest is
> extended posteriorly over the orbit, and anteriorly
> nearly to the snout-tip, highest anteriorly and [most]
> posteriorly.
> 
>   So, there you have it. Aside from the indetirminate
> tooth taxa *Asiamericana* and *Sinocoelurus,* that's
> how my own perceptions fit. I've just finished a
> series of profiles on these spinosaurs, relatively
> sized, and will get it scanned in as soon as possible.

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Please tell me when that's done, I'd be interested in seeing it.

Archosaur J

Jurassosaurus's Reptipage: A page devoted to the study of the reptilia

http://members.tripod.com/~jurassosauridae/index.html

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