RE: Stegosaur volume of Swiss Journal of Geosciences

[Tim Williams <tijawi@yahoo.com>]

Michael Mortimer <mickey_mortimer111@msn.com> wrote:


> Well the postorbital horns were quite distinctive for the
> time, and even now they're almost good enough to be
> diagnostic for Ceratopsidae.  It's only through historical
> accident that Ceratopsidae became a node-stem triplet clade
> that doesn't encompass things like Zuniceratops.  


But how do we know that Ceratopsidae encompasses _Ceratops_?

How many phylogenetic analyses have been done recently that include 
_Ceratops_?  I'm guessing the answer is zero, or very close to it.  


> I'd rather have rule-based taxonomy than judgement calls
> and "experience" any day.  Didn't we have enough
> subjective, authority-based taxonomy in the past?


Yes we sure did.  But that's not what I'm saying here.  I'm simply talking 
about the naming of clades.


Phylogenetic taxonomy is phylogeny-based, not authority-based.  For 
phylogenetic taxonomy it's my argument that family-level clades should be named 
after one of the better-known (scientifically speaking) members of the clade.  
Most families already are: Tyrannosauridae, Allosauridae, Neovenatoridae, 
Coelophysidae, Brachiosauridae, Camarasauridae, Diplodocidae, Stegosauridae, 
Ankylosauridae, Iguanodontidae, Pachycephalosauridae, Herrerasauridae, and so 
on.


But other family-level clades are named after crap genera, like Ceratopsidae 
and Titanosauridae.  Titanosauridae has effectively been abandoned in recent 
papers, because the name-giving genus (_Titanosaurus_) is considered a nomen 
dubium by most workers.  Personally, I think _Titanosaurus_ is probably a valid 
genus; but I also think that based on what is currently known of it, 
_Titanosaurus_ is a poor choice to name a family-level clade after.  So is 
_Ceratops_, for the same reason; but workers still continue to use 
Ceratopsidae, and I'm not sure why.  


Authority and experience can be extremely important in taxonomy.  For example, 
when _Iguanodon bernissartensis_ was nominated to replace _I. anglicus_ as the 
type species for _Iguanodon_, this choice was bas
ernissartensis_ is known from good material, and it's a model species for 
_Iguanodon_.


I don't see why the same process can't be used to decide the names of 
family-level clades, and have them all based on 'model' genera - again for the 
sake of nomenclatural stability.  To give one example, at the moment there is a 
carnosaur clade that includes both _Metriacanthosaurus_ and _Sinraptor_.  The 
ICZN would say that the name of this family should be Metriacanthosauridae 
rather than Sinraptoridae, because the former (as Metriacanthosaurinae) was 
named first.  But _Sinraptor_ is based on an almost complete skeleton, whereas 
_Metriacanthosaurus_ is known only from fragmentary material.  So I would say 
Sinraptoridae is a better name for this clade, because it's founded upon a 
well-known genus.  Sinraptoridae also has the benefit of having a phylogenetic 
definition, which includes _Sinraptor_ as a specifier.  For the purposes of 
phylogenetic taxonomy, I can see no advantage in having Sinraptoridae being 
trumped by Metriacanthosauridae. 
 Robotically applying ICZN rules to phylogenetic nomenclature is often 
downright unhelpful.  It's the workers in the field of paleontology who are 
best placed to decide which genera should give their names to higher clades, 
not the ICZN.



Cheers

Tim