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RE: Stegosaur volume of Swiss Journal of Geosciences



Michael Mortimer <mickey_mortimer111@msn.com> wrote:


> There's always a non-zero chance of this happening for any
> taxon.  That's science.  Maybe Noasaurus will prove
> undiagnostic since it's so fragmentary.  Better get rid of
> Noasauridae in favor of "Masiakasauridae" (since
> Velocisaurus is hardly better).  Abelisaurus is pretty
> poorly known too.  Carnotauridae is the safer way to go. 
> Ornithomimus is based on a few metatarsals and metacarpals
> that may not even belong to the same taxon.  Let's go with
> Struthiomimidae just to be sure.


You know... all these strike me as being REALLY good ideas.  ;-)  


For the sake of stability, I really do think it is better to anchor clades in 
well-known taxa.  And by 'well-known' I mean scientifically well-known (i.e., 
not fragmentary).  


Because family-level clades are named after genera, it is therefore essential 
to use nominative genera that are well-known, because the nominative genus is 
included in the definition.  To that end, I think names like Ceratopsidae and 
Titanosauridae should be abandoned.  Now, I'm not actually asserting that 
_Ceratops_ and _Titanosaurus_ are nomina dubia; I have an open mind as to 
whether either taxon is diagnostic at the genus level.  However, what I am 
saying is that *all* clades should be defined using well-known genera.  


To that end, if it comes to pass that we have Centrosauridae instead of 
Ceratopsidae, and Struthiomimidae instead of Ornithomimidae, and 
Masiakasauridae instead of Noasauridae, and Sinraptoridae instead of 
Metriacanthosauridae, then so be it.  IMHO, stability is more important than 
priority.  Besides, some families should never have been named in the first 
place, especially the ones that were monotypic at the time.


> Much as with the Ceratops and Rapator examples, you don't
> seem to see the need to rigorously demonstrate a taxon is
> indeterminate before passing judgement on it.  


Well, I think it's apparent that it's a bad idea to use _Ceratops_ in the 
definition of any clade.  It's striking that
tudiously avoids any mention of _Ceratops_.  So what do we do?  Include 
_Ceratops_ in the definition, and pretend that it's a 'good' genus?  Or 
eliminate Ceratopsidae altogether in favor of a family-level clade that 
actually includes the name-giving genus in the definition (e.g., 
Centrosauridae)?


> It's quite
> frustrating that paleontologists now seem content to throw
> old taxa into the waste bin without trying to prove their
> validity, which goes against the science standard of trying
> to disprove your own hypothesis before you present it. 


No, I think there are two separate issues here.  Yes, we can give every 
fragmentary taxon a fair shake as to whether or not it is valid (i.e., 
diagnostic at the genus level).  But deciding which genera should be used to 
define clades is a separate matter.  For name-giving purposes, fragmentary taxa 
should be excluded.  I think having Ceratopsidae as a clade of ceratopsians is 
as unhelpful as naming a clade of carnosaurs Rapatoridae (after _Rapator_).  
The fact that somebody has already named Ceratopsidae is not a reason in of 
itself to keep the family alive, IMHO.


> The
> easy way out will indeed result in a lot of obviously
> diagnostic taxa, but at the expense of our predecessors'
> legacy.


Alas, for some of our predecessors, their legacy includes many genera (and 
families) that should never have been named in the first place.  


Cheers

Tim