Re: remains of spinosauridae

["Jaime A. Headden" <qilongia@yahoo.com>]

Mickey Mortimer (Mickey_Mortimer111@msn.com) wrote:

<Thus, I must agree with Sereno that S. marocannus is a junior synonym of
S. aegyptiacus.>

  Once again, referral mus be affirmed by holotypes, not by referred
material except were referred material cannot be in anyway differed from
their types. An example from the above snipped comments. Mickey shows how
the type cervical of *S. maroccanus* compares between *Baryonyx* and *S.
aegyptiacus*, and asserts that referred dentition (which is applied by
geography, not morphology or more complete material, which is lacking)
indicates they are "nearly identical." Rather, the condition of the
vertebrae would appear to show that *S. maroccanus* has baryonychine
vertebrae, or is intermediate between a baryonychine and spinosaurine
morphology; the dentition is questionably associated, as neither the type
cervical nor any cervical material is unquestionably associated with
cranial material; the association of most of the referral is based on the
material being Moroccan in geography, and not Egyptian. Furthermore, as
stated by Stromer at least, the cervical vertebrae lack complete neural
spines, and are broken distally, showing there is no definitive length.
*Acrocanthosaurus*, though not a spinosaurid, shows that much longer
cervical spine lengths _are_ possible for another theropod, and this is an
unknown quantity to compare *S. marocanus* to. Thus, the Moroccan taxon
can only be reasonably compared in this sense to the English taxon; the
Eqyptian form is indistinct, and has different proportions relative to the
centrum and neural spine to the Moroccan, which Mickey was well to
indicate a likely similarity to the English form. Would one not then
conclude that *S. maroccanus* should be referred to *Baryonyx*, rather
than refer *S. maroccanus* to *S. aegyptiacus* on the basis of referred,
non-associated cranial material to imfer the presence of a possibly
congeneric or conspecific form to the Egyptian taxon? Does the jaw not
belong to the same taxon as the rostrum described in 1996 by Taquet and
Russell, SAM 124? What other criteria would indicate the spinosaurine
material from Morocco belong to the same taxon as the Egyptian skeleton?

  Rather, the type is distinct from either, even if perhaps it does not
bear a distinct feature from both, an autapomorphy; is this not robust
enough to offer even a specific variation? Perhaps question how one treats
hypodigms that bear material other than their types, and stop referring
material that are not consistent with their types nor associated in a
manner to pump up the type as a theoretical construct? (Okay, that's a bit
extreme, but at someone, this is employed but some, and the theoretic
reasoning is sound behind this, even if the reasons for referring
close-found material to the same taxon as part of a complex is
supportable, when articulation is not enjoyed in the specimen; take the
type of *Bagaraatan*, for instance, or the bizarrely associated
*Achillobator*, which include odd cranial material with odd postcranial
material, and in the former, there is little material to link the partial
jaw to the hips, the most anterior of the postcrania of the type.)

  I think MUCH more caution in what is considered typical of a species,
and how one treats the types and referred material is in order, and such
issues as has been raised in these few threads (*Spinosaurus*,
*Deltadromeus*, etc.) are just small examples of this quality in
paleontology. It's much easier to imagine more complete complexes of the
remains of an animal than to deal with the incomplete remains we _do_
have; this leads, perhaps, to a psychological dependancy on "filling out"
the material with specimens available, even if the association was not
based on any real material consistency. Its easier, so its permissible.
The fossil record is so incomplete, so we should fill it out to make it
easier to work with. Its not enough to find a small articular, you have to
add partial jaws, and cobble together a skull to make the material fit the
theory (okay, the Piltdown hoax is not the same, but we are getting
similar interpretations coming from unassociated material elsewhere in
paleontology in an attempt to fill in the static holes in our fossil
awareness). At which point is it not okay to say that the *S. maroccanus*
can include so much more spinosaur material found in Morocco? If we find
an allosauroid humerus in the Tafilalt or Kem Kem basins, are we going to
refer this to *Carcharodontosaurus* to fill out our complexes? I hope not.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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

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