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Re: [dinosaur] Ceratopsid (Centrosaurinae: Nasutoceratopsini) from Oldman Formation of Alberta (free pdf)

For what it's worth, I think Avaceratops is valid and diagnostic. It sure isn't 
Nasutoceratops. Some of the supposed autapomorphies and other seemingly trivial 
characters being used to diagnose taxa are indeed questionable, but I'm not 
convinced ceratopsids are overdivided. Dinosaurs were not mammals.

On Wed, 12/14/16, Mickey Mortimer <mickey_mortimer111@msn.com> wrote:

 Subject: Re: [dinosaur] Ceratopsid (Centrosaurinae: Nasutoceratopsini) from 
Oldman Formation of Alberta (free pdf)
 To: "DML" <dinosaur-l@usc.edu>
 Date: Wednesday, December 14, 2016, 12:47 AM
 I was going to comment on this myself, but of course in
 the well-worn opposite direction.  I think the current
 state of ceratopsid nomenclature is unrealistically
 oversplit, where a few differences or million years are
 considered enough to doubt conspecificity
  (ditto for Tschopp's Morrison diplodocids).  Compare
 this to theropods, where there are tons of differences
 between e.g. Tyrannosaurus rex specimens, which are known
 from the lower and upper parts of the Hell Creek Formation,
 as well as the Scollard, Denver,
  Lance, Frenchman, etc. Formations all over the continent. 
 I would call Ryan et al.'s Nasutoceratopsini Avaceratops.
  Notably, Ryan et al. are confusingly contradictory in
 their discussion of Avaceratops.  They first state the
 holotype specimen "ANSP 15800 has three unambiguous
 autapomorphies: Ch 36 (jugal infratemporal process, 1>0;
 absent), Ch 49 (parietal, sharp median
  crest, 1>0; absent), and Ch 53 (marginal dermal
 ossifications on parietal and squamosal, 1>0;
 absent)", but then they say "it is currently
 difficult to diagnose Avaceratops because it appears to lack
 autapomorphies or any unique combination of

  Their conclusion is "As a result, Avaceratops is
 represented only by the type specimen
 (ANSP 15800). This immature individual exhibits no
 undisputed apomorphies, rendering a diagnosis of the taxon
 problematic. Nevertheless, the specimen cannot be attributed
 to any other known centrosaurine, and so the genus cannot be
 synonymized or declared a nomen dubium."
 Which is it?  If it has no autapomorphies or character
 combinations considered taxonomically valid, then it _could_
 be synonymized with Nasutoceratops or alternatively declared
 a nomen dubium if it also couldn't be distinguished from
 other diagnostic nasutoceratopsin
  genera (e.g. maybe the Malta taxon once it's named). 
 But if it can't be attributed to any other known taxon,
 then that must be based evidence which would thus form the
 Finally, why do you continue the myth that ICZN-covered taxa
 like Ceratopsidae are affected by the eponymous genus'
 diagnosability?  Haven't I put enough stakes into
 Wilson and Upchurch's baseless assertion this is the
 Mickey Mortimer