Re: Prosaurolophus species INFO!!

["Jonathan R. Wagner" <jonathan.r.wagner@mail.utexas.edu>]

Alessandro wrote:


> Dear ListMembers, please could someone tell me if the new Horner's species
> of Prosaurolophus, P. blackfeetensis is still valid or if it's a junior
> synonim of P. maximus?

    I don't believe anything has been published on this. This Fall we'll get
to see what Weishamplel, Horner, and Forster think in Dinosauria II: The
Electric Boogaloo.


> I ask this because in his MS.Thesis on the
> Hadrosaurian Dinosaurs of the Big Bend
> Texas, Dr. Wagner

I'm not a doctor yet! ;)


> suggested that the two characters used by Horner (1992)
> are due to crushing of the type skull of P. blackfeetensis, than to real
> difference.

I wouldn't go with information you see in a M.S. thesis, as a general rule,
unless it has been published or is referenced as being in the thesis by its
original author in a published work. This is not meant to slight the work
that goes into a thesis; very often they are conducted with limited data,
and sometimes the conclusions are a bit more tentative than what might go
into print (where normally peer review might catch weaker inferences). For
example, some of the conclusions in my thesis are awaiting confirmation by
direct examination of the specimens (part of which I am about to do).

For those who are interested, here is the relevant section of my thesis:
----------------------------------------------------------------------------
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"Prosaurolophus" blackfeetensis, was erected by Horner (1992) on a subadult
type specimen and distinguished by two characters. Of the two characters
offered in support of this species, the greater rostro-caudal length of the
nasal crest in "P." blackfeetensis appears to be due partially to crushing
of the type skull, in which the prefrontal has been displaced ventral to the
skull roof, which in turn has been rotated dorsally and laterally,
accentuating the juvenile frontal dome and appearing to elongate the crest.
Isolated nasals from adults (Horner, 1992, plate 29 A and B) show that the
caudal margin of the crest was abrupt, and the rostro-ventral length short
in adult animals.

The other character, lack of expression of the circumnarial fossa on the
prefrontal, again appears to be the result of crushing in the type, as is
the apparent lack of a prefrontal ridge. The prefrontal is illustrated in
its crushed orientation, rather than in life position. In life it would have
been inclined dorsolaterally, and the broad fossa visible on its dorsal
surface in photographs would be continuous with the circumnarial fossa.
Since only the prefrontal of the type is illustrated, it is impossible to
determine the situation in an adult of the putative species. The lateral
margin of the circumnarial fossa illustrated on adult nasals (Horner, 1993,
plate 29 A and B) appear to show the exclusion of the prefrontal from the
fossa. However, this ridge is very similar in morphology to that
observed in Saurolophus maximus (Brown, 1916A), and without a prefrontal
there is no support for this character. Thus, "Prosaurolophus"
blackfeetensis is not distinct, and is here considered a junior synonym of
Saurolophus maximus.

------------------------------------------------------------------------

Wagner

P.S. I should mention that Alessandro contributed greatly to my MS research
by helping to scrounge up a hard-to-get Italian reference.