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Re: Stonesfield theropod OUM J13506



On the ongoing Stonesfield problems (how British of me):

Stephan Pickering (stefanpickering2002@yahoo.com) wrote:

<Compared with the ceratosaur Walkersaurus hesperis BMNH R332, it has a
very different shape, the subnarial plate differs in reaching the
premaxilla laterally. The nasal process is less far back. The height of
the caudal plate decreases less gradually. The recess is shallower. There
are 11 teeth in 320 mm vs. 11 in 250 mm, but the teeth are larger and so
are more crowded. The teeth differ in the mesiolateral bulging and basal
medial thickening. The 4th vs. 5th tooth is below the centre of the nasal
process.>

  It is very peculiar to hear of *"Megalosaurus" hesperis* being a
ceratosaur, and I would very serious like to know what is concluded to its
status as a ceratosaur?

<Currie and Zhao in 1994, positioned Yangchuanosaurus in Sinraptoridae, on
the basis of the "arrangement of the accessory fenestra in the antorbital
fossa", but did not, of course, analyze the hypodigms of the
Megalosauridae as I have constituted it.>

  I could detail Currie and Zhao's actual diagnosis for Sinraptoridae and
detail the list of characters both *Y. shangyouensis* and *S. dongi* share
to the exclusion of other basal tetanurans, but it would go on. The study
was a result of over several years of research after the two supervised
the excavation of the type Chinese taxon. This is saying much for one whom
is not very arguably the best expert on theropods extant (Welles'
expertise was not, despite claims, on theropods), being Phil Currie.
However, the diagnosis in the mandible went beyond generalized fossae in
the maxillae, but involved a complete invagination with unique maxillary,
confluent nasal fossae, fenestrae, internal chambers, medial laminae,
maxillary fenestra position, maxilla shape, tooth size and arrangement,
and so forth. As yes, they did not analyze Stephan's hypodigms because he
did not, at the time, ever present them, and nor do I think it would have
worked: Currie and Zhao, however, did in fact compare the forms to work by
Britt on *Torvosaurus*, used Dong et al's work on *Yangchuanosaurus*,
Gilmore's and Madsen's on *Allosaurus*, etc. More recent work, including
that of Holtz in 1994 and 2000, reviewed the relativity of *Baryonyx*, and
now we have *Afrovenator* from Sereno et al. and Allain on
*Streptospondylus* with Chure on *Poekilopleuron*. Chure is also reviewing
on other taxa, and a monophyletic and very robust clade of Sinraptoridae
is in evidence.

<Recent efforts to use Megalosauridae without Megalosaurus bucklandii are,
needless to say, not tenable.>

  Allain did not give reasons to using Megalosauridae, so any argument is
fairly weak. Only Allain has used Megalosauridae to label this group in a
phylogeny, and this is where we must consider the issue. It is a component
of science that provability be entered without prejudice, and that work be
evaluated on its own merits, not on "intents" and so forth of why things
are used without verification.

<Not acceptable, too, is the opinion that Megalosaurus bucklandii must be
restricted to Buckland's mandible (neither Buckland nor von Meyer chose a
type specimen; it is OUM J13505, the rostral right dentary + the
kleptotype specimens listed below), nor do I accept the opinions that
Buckland's original figures of a partial skeleton are not from the same
individual.>

  And still the evidence is shaky, based on a single quarry ... to my
knowledge, all the Stonesfield elements are the same color and
preservational condition, implying a similar burial period, and being of
similar size means nothing if in fact gregarious animals are involved or
its a common kill site, as in some Utah or Alberta localities. And
appologies to the memory of Sam Welles, but he is not a paleo deity. Any
professional can be wrong, just as I may be [not a professional, but I can
still be wrong, and perhaps more so as I am only a student :)]. It is
certainly problematic to be relying on the word of a manuscript or set of
them, never published or subjected to review or verification from experts
in the field.

<Megalosauridae consists of Megalosaurus (including Torvosaurus),
Metriacanthosaurs, Eustreptospondylus, and Poecilopleuron/Poekilopleuron
(the former spelling, it seems to me, will prove to have priority, as the
earliest publication I am aware of uses it, although I am still awaiting
word on elusive pre-1838 abstracts).>

  I recently have found that no type was designated for *Therizinosaurus*,
reflecting on the then current ICZN dictum where a type must be designated
to validate a name and usage, but this has been assisted by follow-up work
by Maleyev who used the specimens numbers as the type, but not in any
designatorial work. The first major paper discussing the claws and
indicating the type was by Barsbold, so does this mean that Barsbold
carries the name? The first reference work on *Poekilopleuron* (and I have
his first) by Eudes-Deslongchamps with a specimen allocation and figures,
is the monographic work, and frankly, the spelling is clear in the title
despite the fact that the name is treated as having been coined previous
to the work. Still, one may then just use the monographic work as the
first valid allocation of a name, description, comparison, and type
designation with illustration and therefore the date carried in the work.
I need to check on Allain and Chure and see how they treated the subject
in their historical review.

  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.

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