RE: Sereno's (2005) new definitions

[Michael Mortimer <mickey_mortimer111@msn.com>]

Tim Williams wrote-

> > Not so.  You can run the Troodon formosus holotype premaxillary tooth in a 
> > matrix as an OTU.  In fact, it's easy to do such because there are so few 
> > characters to code.
>
> I see what you mean.  Using that criterion, many nomina dubia could be put 
> through a matrix so long as at least one codeable character is discernable. 
>  But it was my impression that a nomen dubium could not be used in a 
> phylogenetic analysis on account of the fact that it has no taxonomic 
> standing, and so cannot be a valid operational taxonomic unit.  In other 
> words, the T in the OTU is missing - although as Mickey showed, you can 
> still carry out the O part.  But I don't think it's worth the effort.

But a nomen dubium is just a specimen, an organism.  So if we can run more 
diagnosable specimens through phylogenetic analyses, why not less 
diagnosable specimens?  AMNH 460 has no taxonomic standing, yet Upchurch et 
al. (2004) ran it as an OTU.

> Putting a nomen dubium in a matrix is entirely artificial - and maybe a bad 
> thing to do if the resulting phylogeny is influenced by the inclusion of 
> nomina dubia.

A nomen dubium cannot influence a topology except to create a polytomy which 
covers its potential placements.  Only taxa with unique combinations of 
characters can influence topologies, but nomina dubia by definition lack 
those.

> In other words, we could put a nomen dubium into a matrix - but why would 
> we need to?  Why, when we could just replace the nomen dubium with an 
> unquestionably valid taxon?

To tell what the nomen dubium's phylogenetic relationships are, of course.

> Ceratopsidae should be junked too, given that _Ceratops_ is probably a 
> nomen dubium (and unlike _Troodon_, we would be hard-pressed to find its 
> position in ceratopsian phylogeny given the _C. montanus_ type material).  
> The name Hadrosauridae is unhelpful, given the status of the _Hadrosaurus_ 
> type specimen.  If we are serious about erecting definitions that are 
> stable, then some time-honored traditions have to be compromised, ICZN or 
> no ICZN.  Ceratopsidae could become Centrosauridae, and Hadrosauridae could 
> become Saurolophidae - but Ceratopsia and Hadrosauria would remain.

Why view -idae and -ia clades differently if we're ignoring the ICZN?

Mickey Mortimer