RE: Platecarpus tympaniticus - how to analyze a nomen dubium

[Tim Williams <tijawi@yahoo.com>]

Anthony Docimo <keenir@hotmail.com> wrote:


> > *Ceratops*: has anyone even looked at the material in
> > the last couple of decades?
> 
> Wait....if nobody's looked at the material, what has this
> discussion been running on?  (theory and ideals?)


Don't panic Anthony.  Penkalski and Dodson (1999) provide a fairly detailed 
description of the _Ceratops montanus_ type material.  So does Ryan (2007).  
Both studies regard the _Ceratops montanus_ material as non-diagnostic at the 
genus or species level, and therefore the name _Ceratops montanus_ is a nomen 
dubium.


I'm not actually endorsing the view that _Ceratops montanus_ is a nomen dubium 
(though I suspect it is).  My argument is that given the meager remains, 
_Ceratops montanus_ is a poor choice to name a family after.  Both the ICZN 
Code and PhyloCode agree that the family Ceratopsidae must include _Ceratops 
montanus_.  Thus, Ceratopsidae must be defined such that it includes _Ceratops 
montanus_ as a specifier.  But because _Ceratops montanus_ is unlikely to 
contribute anything meaningful to a phylogenetic analysis, _Ceratops montanus_ 
is unlikely to be used to anchor any clade (including Ceratopsidae).  Ergo, 
_Ceratops_ should NOT give its name to any family-level clades (e.g., 
Ceratopsidae, Ceratopsinae, Ceratopsoidea).


>  Except none of us are precognitive -  we don't know
> that better species will be found.  (we hope they will,
> but its not a guarantee)


Mike Taylor answered this better than I ever could, but it's worth emphasizing 
the point that suprageneric taxa should not be erected for a single genus.  
This used to be common practice, but it's totally unnecessary, and frequently 
unhelpful.

 
> okay, let's say that, twenty years from now, I discover a
> dinosaur that is as related to other Archosaurs as the
> Pangolins are to other Mammalia.


This assumes that ranks (phylum, class, order, etc) have some intrinsic 
quantitative value.  But they don't, and never have.
  

Consider this: All those many bird "orders" (Struthioniformes, Falconiforme
vialae.  The Avialae is in turn a clade within the Maniraptora, which is a 
clade within the Theropoda, which is a clade within the Saurischia.  Yet, 
Linnaean taxonomy lists Saurischia as an "order".  Take-home message: Linnaean 
ranks are a world of pain.



Cheers

tim