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Re: Spines (Re: Texas dinos)



M Mendez wrote-

> I find Rauhut's theory to be fallacious. Stromer 1915
> attributes the remains of a large theropod found near
> a hill to one individual. Mike was the first to share
> this with me, however, I think, morphogically, spines
> over six feet in height could not work on such large
> theropods as are carcharodontosauroids (especiallly
> such laterally compressed neural spines). Aside from
> that, Stromer figured the spines and the centra for
> Spinosaurus which show an almost circular centra
> rather than an ovalish one like the one in
> _Carcharodontosaurus_. (I think the fact that the
> neural spine and the centra are not fused (as shown in
> the figs.) suggest this individual was not fully
> mature.

As Josh pointed out, Spinosaurus was still very large (I estimate 17.4
meters long), whether it was allosauroid or not.  Okay, technically
allosaurids have differently proportioned bodies, so a 210 mm long posterior
dorsal would make an allosaurid Spinosaurus 14.7 meters long instead.  Still
just as large as Carcharodontosaurus.  As for vertebral proportions, no
one's arguing Spinosaurus was synonymous with Carcharodontosaurus.

> Regarding the relationship of _Acrocanthosaurus_ to
> _Carcharodontosaurus_, Currie and carpenter 2000
> suggest that it (Acro) fits into Allosauridae and not
> in Carcharodontosauridae. Contra Currie,
> Acrocanthosaurus is united to Carcharodontosaurus by
> such features as the prominent postorbital, the
> tapering jugal+quadratojugal as well as squamosal. (to
> name a few)

Currie and Carpenter point out the orbital shelves of Acrocanthosaurus and
carcharodontosaurids are made of different elements, so are not homologous.
They also show the orbital process of the postorbital is absent in some
Acrocanthosaurus specimens.  Acrocanthosaurus lacks a ventral extension of
the basisphenoid and a ventrally expanded dentary symphysis.  The wide
cerivcal centra are not found in Giganotosaurus.  Acrocanthosaurus also
lacks caudal pleurocoels and a larger pubic boot than allosaurids.  Although
they do not actually say what characters place Acrocanthosaurus in the
Allosauridae, I ran their matrix in PAUP to find out.  The following are
supposed allosaurid synapomorphies-
1. promaxillary and maxillary fenestrae present
2. basioccipital participates in basal tubera
3. distal ends of paroccipital processes below foramen magnum
4. separation of trigeminal (V) nerve branches complete
5. internal carotid opening pneumatized
6. long basipterygoid processes
7. reduced external mandibular fenestra
8. axial intercentrum subparallel to axis ventral margin
9. paired anterior and posterior processes at base of chevrons
10. pronounced notch between acromion and coracoid
11. sigmoidal humerus
12. metacarpal IV absent
13. pubic foramen present in distal pubis
Several of these look plesiomorphic.  I think using more basal tetanurines
would have helped (eg. Fukuiraptor, Torvosaurus, spinosaurids,
Piatnitzkysaurus, Eustreptospondylus, Neovenator).
Holtz (2000), who did include more taxa, found Acrocanthosaurus was a
carcharodontosaurid, based on-
1. lacrimal suborbital bar
2. frontals fused
3. broad postorbital-lacrimal contact (invalid)
4. orbital process on postorbital (invalid)
5. basipterygoid processes moderately long
6. anterior face of midcervical centra elevated
7. caudal pleurocoels (invalid)
8. cervicodorsal hypapophyses absent
9. sacral pleurocoels
10. humeral head offset and emarginated ventrally by groove
11. deltopectoral crest expanded and offset from humeral shaft
14. anterior ramus of maxilla shorter than tall
Maybe Tom will tell us where Acrocanthosaurus is currently falling out in
his analysis....

Josh Smith wrote-

> This individual was also very likely a
> subadult its true, but an adult _S. aegyptiacus_ was very likely very
> similar in size to an "average" sized individual of
> _Carcharodontosaurus_.

But if the subadult holotype of Spinosaurus was about 17 meters long (12-19
tons), how can the adult be similar in size to Carcharodontosaurus (~13 m,
5.5 tons)?

Mickey Mortimer