[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Ceratosauria vs. Neotheropoda?



Gregory S. Paul <GSP1954@aol.com> wrote:


> Nein, nein, nein. Hadrosauriformes are not a subset of
> iguanodonts, both are subsets of iguanodontoids. 


Ja.  Hadrosauriformes and Iguanodontoidea are effectively the same clade, 
albeit defined differently.  

Hadrosauriformes = Least inclusive clade containing _Iguanodon_ and 
_Parasaurolophus_. 

Iguanodontoidea = _Iguanodon_ and all iguanodontians more closely related to 
_Edmontosaurus_ than to _Camptosaurus_.  

Thus, hadrosaurids are a subset of Hadrosauriformes, as are your "classical 
iguanodonts" (_Iguanodon_, _Mantellisaurus_, _Dollodon_) that you mention in 
the Cret Res paper.  However, whereas the Hadrosauridae form a clade, the 
"classical iguanodonts" (your Iguanodontidae) do not (at least, not to the 
exclusion of Hadrosauridae).  


> What we have now is a situation in which your 
> hadrosaurs have series of formal names pertinent to them
> alone because of the accident of their being derived within the clade,
> while the more basal iguanodontoids are stuck with no formal 
> designation because doing so would result is gasp and horror
> paraphyletic groups which are phylocode evil for no 
> good reason. 


Well, as you yourself say in the paper, the "classical iguanodonts" do actually 
have a formal designation:


     "The only cladistic designation for iguanodonts below the
     _Ouranosaurus_-hadrosaur clade is the unwieldy "non-hadrosauroid
     iguanodontoids", in which the members are described by what they 
     do not belong to as much as what they do belong to."


Thus, the formal designation for classical iguanodonts is "non-hadrosauroid 
iguanodontoid" or "non-hadrosauroid hadrosauriform".  So the issue here is not 
whether there is a formal designation for a group that includes _Iguanodon_ and 
friends, but whether you like this particular designation.  You find it 
"unwieldy", and would prefer that the term "Iguanodontidae" be used for this 
group.  Fair enough.  But there is nothing discriminatory or unfair about this 
'cladistic' approach.  The usage of these 'cladistic' terms merely documents a 
shift from a rank-based classification whereby all genera could be neatly 
sorted into families, to a phylogeny-based classification whereby only clades 
are recognized as valid categories.  That's all.  

In short, it comes down to aesthetics and personal preference.  I don't mind 
"non-hadrosauroid hadrosauriform".  You do mind (very much so), and would 
prefer "iguanodontid".  


> Having just finished up the dinosaur field
> guide I cannot 
> overemphasize how this is a taxonomic mess that will
> befuddle the public. 


The "taxonomic mess" is solely a consequence of trying to translate a cladogram 
into a rank-based classification.  In principle, I don't have any grudges 
against paraphyletic groups.  But I have concerns that Iguanodontidae and 
Hadrosauridae will be treated as sister taxa, because the important distinction 
between a grade (paraphyletic) and a clade (monophyletic) is lost in 
translation.  The 'cladistic' terminology may be unwieldy, but at least it is 
explicit.

Cheers

Tim