RE: SPINOSAUR SYNONYMY

[Adam Yates <A.Yates@zoo.latrobe.edu.au>]

>This message may be a little premature, seeing as the 13 Nov 98 Science
>hasn't
>arrived at the UW library as of yet, but I feel I must take issue with
>some of
>Sereno et al's synonymies.

>First off, they sink Cristatusaurus lapparenti into Baryonyx walkeri.

Not exactly. Its a subtle point but they say that no distinguishing features
of C. lapparenti can be found thus in their opinion it cannot be
distinguished from Suchomimus or Baryonyx (the material is certainly not
spinosaurine). It was Charig and Milner who placed the C. lapparenti (not
named at the time) material into Baryonyx. Given that C. lapparenti is based
on undiagnostic material (a debatable point) it becomes a nomen dubium. 
Is Cristatusaurus a nomen dubium? Personally I don't think so. It lacks the
derived premax characters that diagnose the Spinosaurinae so it probably
belongs to the Baryonychinae. I think it is distinguishable from Baryonyx,
but not from Suchomimus with which it shares some characters (more pointed
rostral apex to premaxilla vs. rounded in Baryonyx and a sagital crest
present on the premaxilla. Therefore I believe that Cristatusaurus
lapparenti is the senior synonym of Suchomimus tenerensis.

>As for Tom's suggestion that Taquet and Russell's S maroccanus snout
>almost
>certainly belongs to Suchomimus...  The snout assigned to S maroccanus
>has a
>distinctive pattern of premaxillary dentition.  Tooth one is small,
>teeth two
>and three are large and paired up, teeth four and five are smaller and
>paired,
>and six and seven are small too and paired up.

Agreed, the snout illustrated by Taquet and Russell is certainly NOT
Suchomimus, it is clearly spinosaurine (the 1st premax tooth is
reduced,there appears to be a diastema in the premax tooth row, and the
external naris is shifted posteriorly). As for the last feature I think it
is suprising that Sereno et al. noted that it was currently an autapomorphy
for Irritator, that may eventually be found to diagnose the Spinosaurinae,
when this Spinosaurus snout clearly has the derived condition. 

cheers
Adam Yates