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Re: Validity of *Suchomimus*



I wrote: 

 <Part of the _S. tenerensis_ material consists of an articulated snout.
Unfortunately, the
C. lapparenti material is incomplete.>

 Jaime A. Headden wrote:
<  ... but comparable ...> 

Although both _S. tenerensis_ and _C. lapparenti_ are from Gadoufaoua,
they may have
some different characteristics. 

 <But Taquet and Russell (1998) do, and figure two of them (there are
three) as well as
the additional maxillary and dentary material.>
 
They do describe the two specimens, is the third badly preserved? The
pictures of GDF
365 and 366 are not so good in this paper, but Keller and Campos (1996)
do present
stereopairs which are more useful. 

  <On premaxillary hookedness: *Baryonyx* possesses a more hooked premaxilla
in
profile than other baryonychines: it is shallower posterior to the third
alveolus than at it,
which is similar to the condition in *S. maroccanus* [I really dislike
Sereno et al's
lumping this species in with the type species, the jaws _do not_ match,
and the vertebrae
are quite distinct] -- the longirostrine condition. This hookedness is
reduced in
*Suchomimus* (MNN GDF 501) and *Cristatusaurus* (MNHN GDF 365, 366) --
the
brevirostrine condition -- where the premaxillae deepen posteriorly.
>

Note:
_S. maroccanus_ has it?s widest point in the premaxillae in the third
alveolus. In dorsal
view, _S. maroccanus_ has somewhat of a wide premaxilla. The specimen
is long, low
and narrow. The alveoli are paired off in two, it contains 7 premaxillary
teeth. Becaus eit
is low, i would think that it makes it a Spinosaurine, this is because
of the retracted nares,
they seem to be placed further back than in Baryonychids. 

_B. walkeri_ , in lateral view, is not hooked greatly. It does have it?s
shallow point in the
third alveolus, as apppears on _S. maroccanus_. Over looking at specimens
GDF 365 and
366, they seem to have their shallow points in the premaxilla. GDF 365
seems to have
more of a shallowness than GDF 366 has. GDF 366 is flat, in lateral view
that is.
GDF 365 = (_--_  .......  GDF 366 = (____
Both seem to have the shallow point on the fourth alveolus, unlike other
spinosaurs that
have it on the third. (the picture quality is not the best, i have a
photocopy) 
I cant seem to tell where the shallow point on _S. tenerensis_ is. 

<Marco's statement that either *Cristatusaurus* statement is incomplete
at the maxillary
does not relate to the fossils, which bear slight sutural surfaces for
the rostral lobe of the
maxilla, and the medial maxillary process of the premaxilla is apparent
in GDF 366. The
ventral extent of the bone in the anterior portion of the premaxillae
are not entirely
preserved, being partially eroded, and so may have indicated more depth
anteriorly. The
smaller, type specimen is more hooked in profile than the larger one,
of all things, but the
larger specimen is more rugose, and perforated by many more foramina,
and the base of
the nasal crest bears a large groove and foramen, as in *Suchomimus*
and *Baryonyx* --
the region is not preserved in GDF 366 or other spinosaurines.>

I am looking at the paper, you must mean; the big one [GDF 365] is more
hooked in
profile than the smaller one. If not, we?re both making continous errors.
I am looking at
the Taquet et Russell (1998) paper. GDF 365 [the large one] is more rugose
than the
holotype [the smaller one; GDF 366]. GDF 265 does seem to have a groove
at the top,
which GDF 366 doesn?t have. This leads me to wonder.....as the individual
matures, does
the premaxilla become more hooked???

See, both _S. tenerensis_ and _B. walkeri_ are sub-adults, and they?re
not hooked so
much at the maxilla. Both are Baryonychids, so is _C. lapparenti_. GDF
366, the young
individual, has a rather almost flat premaxilla [in lateral view].  ie:
(___


   <Au contraire, mon ami. Es possible. The larger specimen is virtually
identicle to
*Suchomimus,* and in any case that the holtype cannot be referred, the
referred snout
can. There are no differences, except of the spacing of the alveoli,
that I can discern.
Even the secondary palate is identical, while it is smooth in *Irritator*
and deeper
posteriorly in *Baryonyx*. In any even, the holotype is closer in morphology
to
*Suchomimus* than t *Baryonyx*, and morphology is not as distinct as
is being
suggested, when individual variation has not, in my opinion, been taken
into account.>


Ahh, mon ami, regarde ce.... The larger specimen might be identical in
some
characteristics,  but not the same. Look at GDF 365 and 366, the anterior
part of the
premaxilla; it gets narrow [look at fig. 5A and 6A; in Keller and Campos
1996]. Then
compare to a Spinosaurine, the anterior part of the premaxilla gets narrow,
this also
happens in _Baryonyx walkeri_ [Fig 2A Charig and Milner 1997]. This narrowness
happens in _S. tenrensis_, but not at the extent of GDF 365 et 366. 

>From dorsal view, GDF 365 et 366 seem kinda rounded. While _S. tenrensis_
?s
premaxilla seems squared, not so much. But it is not as rounded as _C.
lapparenti_ is.   
_B. walkeri_has the similar charcteristic as does _C. lapparenti_. 
The spacing between the teeth are of different sizes. Again, that is
an individual
characteristic, it is different in all animals. 
Morphology is similar in Baryonychids.



<The published paper on *Suchomimus* gives no reasons to supplant 
*Cristatusaurus*
or reduce its affirmation as a valid taxon. This is what they (Sereno
et al.) should have
done. This could have been stated in the back, as was done in that paragraph
for
"Spinosaurus B" being knocked into *Carcharodontosaurus* -- reasons where
listed by
comparison to other taxon. Pick up the paper and "Ahhh..., I see his
point." You can only
wonder why *Cristatusaurus* was simply discarded as a _nomen dubium_.>

This is not a very long paper, it does have it?s high and lowpoints.
I cannot state a reason
n why the authors did not give reasons to pass _C. lapparenti_ as a nomen
dubium (but I
can ask). I have read that section many times, it does give statements
which seem clear to
say, this dinosauris different that ours and someone said it belongs
that species. That is
what it basically says. 
>From Sereno et al. (1998) :
?The authors state that the material differs from _Baryonyx walkeri_
by the ?breviostrine
condition of the premaxilla?. However, no ditinghishing features or proportions
are
apparent to us or previous authors?

I am not so familiar with how naming works, but I do know this:
?If a taxonomist decides that the type specimen is inadequate to tell
if the species is
really distinct, he or she may sink the species name as a nomen dubium
(?doubtful
name?)? --from ?Bringing Fossils to Life?  by D. Prothero.  
I would think this is why _C. lapparenti_ was passed off as a nomen dubium.
Also, Charig and Milner (1997) had already passed both specimens [GDF
365 and 366]
off as indeterminate species of Baryonyx. 

I do agree with this next statement. To me it would seem that if a species
is named, the
author(s) would be acreful in claiming a new taxon. So many new species
are being
described. I would think that the paper is reviewed many times before
it is published, but
errors can be made. 
<This is why clarity in describing and reducing taxa should be handled
with the utmost
care.>

<Most spinosaurs as known with this material lack this region except
*Baryonyx* and
*Suchomimus*, and that of *Irritator* is badly eroded and anything dorsal
to a thin strut
above the external nares is absent.>
We need more spinosaurs. 

< I think quantifying the skull characters will have to wait until *Irritator*
is fully
described. >
Any idea when? I heard Hans Dieter-Sues was working on it. 
I know Milner is working on some more Spino stuff. 

< The bulbous vs. hooked may be better discarded, as seen above: *Baryonyx*'
premaxilla is more similar to *S. maroccanus* than to *Suchomimus* or
*Cristatusaurus*. Teeth of course are serrated vs. not serrated, but
some basal
spinosaurine may come along and say "Look Ma! I got *Ceratodus* stuck
in my
serrations!" Sail height is really equivocal, Sucho has a taller sail
than Bary, and the *S.
aegyptiacus* has one even taller. Relative density of teeth in the lower
jaw is also
equivocal because no spinosaurine has both a lower jaw and an upper that
both bear
teeth; *Cristatusaurus'* lower jaw may have less teeth than *Baryonyx*,
but this is very
dubious without a more complete jaw. Primary characters are in the teeth,
I would think,
until more complete spinosaurines are known. I also need to get the *Baryonyx*
monograph to compare *Spinosaurus'* vertebrae....>  

Another character might be the teeth spacing. By this I mean; some Spinos
do have a
good amount of spacing between their teeth, thus the number of teeth
is lower or higher. 
Neural elongations; some spinos may have small elongations [or none],
while others have
a big huge sail like _Spinosaurus Aegyptiacus_. 
As any group, a basal taxon is needed. Characters now may just be skull
features, on
some it may be vertrebra, but more complete specimens are needed. 
We should go get us some spinos ay?  


  < I would expect the number to vary, personally, within the jaw. A
mean or the relative
count rostrocaudally and top and bottom may be the best way to count
these. Anyway,
Sereno et al.'s figure of the tooths gives a variable on the 5-6 serrat./mm
size, which is
lower than that in *Baryonyx* (7) as given by Charig and Milner (1990),
and equal to
that of *Cristatusaurus* (5-6; see above). Again, I would caution the
use of serration
density without quantifying this count in the jaws. >

In my opinion, the number of teeth is a better character than the number
of serrations. 

  < *Suchomimus*, per Sereno et al., 1998, has "textured enamel surfaces"
(pg. 1298)
which are not comparable to photos of other teeth I've seen, but I haven't
seen
*Baryonyx* up close, yet. These ridges are not flutings, but longitudinal
wrinkles, and
the literature is clear with photos that fluting in spinosaurids does
not correspond to little
wrinkles, but long fluted surfaces. >

Yes, _S. tenerensis_ and _Baryonyx walkeri_ do have the ?wrinkles?. All
running along
the tooth, not across. They are numerous and give the teeth a textured
surface, instead of
a smooth surface.

<Spinosaurines bear longitudinal ridges, perhaps better developed than
baryonichines,
and are immediately discernible in *Irritator* (see Kellner and Campos,
1996: fig. 2B)
and *Spinosaurus aegyptiacus* (Stromer, 1915: taf. I) has very well developed
and
discernible ridges and grooves prompting the utility of these ridges
to diagnose
*Siamosaurus* as a spinosaur. Who knows, may there is a Thai spinosaur....>

The drawings of the teeth of _Spinosaurus Aegyptiacus_ are well done,
a smooth ridge
can be seen that runs along the side of the teeth, somewhat like a crocodile?s
tooth. The
teeth are not greatly textured as in _S. tenerensis_ and _B. walkeri_,
it may just be the
photocopy, but overall they seem smoother. There are 16 teeth in the
lower jaw of _S.
aegyptiacus_, 32 in both jaws. There is that character that the teeth
are paired off. 

Thai spino ay..... is this mentioned in one of the spino papers?
I also know that Taquet et Russell mention about the coonsideration of
_Pelicanimimus_
as a spinosaur, hah?, isn?t _Pelicanimimus_ an ornithischian????

-Marco A. Mendez

-- 
Marco  Mendez
spinosauroidea@onebox.com - email
(773) 377-5006 x2159 - voicemail/fax
AIM: spinosauroidea
"we all live in a yellow submarine" -The Beatles

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