Archaeoraptor v Microraptor

["Tim Williams" <twilliams_alpha@hotmail.com>]

T. Mike Keesey wrote:

> I remember asking this list a while ago what the difference between _nomen
> dubium_ and _nomen vanum_ was. The upshot seemed to be that _nomen vanum_
> didn't really mean much, and _nomen dubium_ should be used instead. Is
> this right?

As I recall, "nomen dubium" refers to a name that is dubious for ANY reason. 
 "Nomen vanum" refers specificaly to a name that is invalid because the 
type specimen was inadequate for diagnosis.  There was an article in the 
_Journal of Vertebrate Paleontology_ which discussed this in depth.  (If I'm 
wrong about this, then I invite corrections.)

> At any rate, it seems that if _A. liaoningensis_ and _M. zhaoianus_ are
> based on the same *individual*, what goes for one goes for the other.
> Unless I'm mistaken, if Olson's designation is to be invalidated it must
> be in some other fashion.

I'm not certain about this interpretation.  _Archaeoraptor_ and 
_Microraptor_ may be based on the same *individual*, but one could say that 
they are based on different *specimens* (slab and counterslab).  Slab and 
counterslabs of the same individual may or may not receive the same catalog 
number - in the case of _Microraptor_ they happened to be catalogued 
together.  Many other individual fossils have counterslabs (e.g. 
_Scleromochlus taylori_, _Sinosauropteryx prima_) and it at the discretion 
of the museum (or whatever place the fossil is being housed) whether slab 
and counterslab are catalogued under the same number.

The other issue concerns what happens when earlier-named non-diagnostic 
material is shown to belong to a later-named specimen that is diagnostic.  
Does the name of the former take priority over the latter?  This may have a 
precedent:

http://www.cmnh.org/fun/dinosaur-archive/2000Jun/msg00295.html

In this case, the crappy type specimen of _Manospondylus gigas_ might be one 
part of a more complete _T. rex_ specimen.  Does this mean that this latter 
specimen must take the name _Manospondylus gigas_?  If it does, then it 
means that we have a diagnostic specimen that carries the name 
_Manospondylus gigas_.  This would further mean that the name _Manospondylus 
gigas_ would have priority over _T. rex_.  My recollection of the discussion 
on the list that this story sparked regarded this proposition as absurd.  
The name _Manospondylus_ is attached to a non-diagnostic vertebra, and 
should be limited to this vertebra irrespective of whether this vertebra 
belongs to a more complete (and diagnostic) specimen of _T. rex_.

Similarly, in the _Archaeoraptor_ vs _Microraptor_ fracas, we have one 
*part* of the specimen (the tail vertebrae) carrying the name 
_Archaeoraptor_ and the whole specimen carrying the name _Microraptor_.  If 
the tail vertebrae are non-diagnostic then, like _Manospondylus_, 
_Archaeoraptor_ can be put to bed as a _nomen dubium_.


Tim




------------------------------------------------------------

Dr Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163

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