Re: "Megapnosaurus" says farewell...

["Steve Brusatte" <dinoland@lycos.com>]

On Wed, 13 Feb 2002 00:02:24  
 Dinogeorge wrote:
In a message dated 2/4/02 5:09:11 PM Pacific Standard Time, 
   dinoland@lycos.com writes:

<< There is absolutely nothing to designate whether two animals should be put 
   in the same genus or two separate genera.  I mean, if I wanted to I _could_ 
   place _Syntarsus_ (the beetle!) and a rabbit in the same genus.  Who would 
   stop me?  It may seem ridiculous...but there is no convenient definition, a 
   la species. >>

>Well, then your genus, since it would have to be a clade, would also include 
>   all other arthropods, all chordates, and a bunch of other invertebrate 
> phyla. 
>   These would, for convenience, have to be subdivided into subgenera, 
>   subsubgenera, and so forth. So eventually you'd be back where you started, 
> only at a different taxonomic level.

Yes, exactly.  I'd be back where I started: a taxonomic mess.  Certainly 
recognizing two genera in this instance (_Syntarsus_ and any genus of rabbit I 
choose) would be more convenient, as it would minimize the messy subgenera, 
etc.  But, it is still as subjective as grouping rabbits and _Syntarsus_ into 
the same genus.  Convenience, like subjectivity, shouldn't be what guides 
scientists.  Otherwise, Avogadro's number could be designated as 6.0 x 10^23.  
Convenient?  Yes.  Correct?  Only partially.    

><< I have never quite understood why _Psittacosaurus_ has something like 
>seven or eight valid species, but _Coelophysis_, _Syntarsus_ (Raath), 
>_Eucoelophysis_, etc. were placed in separate genera.  It's aesthetic 
>philosophy, not science sensu stricto. >>
>
>So far nobody has been able to come up with a consistent way to group 
>together the various species of Psittacosaurus. You either have x species or 
>x genera. They all look enough alike that the species level is considered 
>more appropriate.

Exactly.  Nobody has been able to subjectively come up with a consistent way to 
group the species of _Psittacosaurus_ into anything but one genus.  In this 
case, as George said, the species level is _considered_ more appropriate.  
However, there is no widely-accepted definition or principle that merits this.  
I think we all know that.

Regards,
Steve

****
Steve Brusatte
Dino Land Paleontology
http://www.geocities.com/stegob
****


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