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Re: Type material: does it have to look pretty?



In a message dated 97-11-26 18:02:58 EST, bh162@scn.org writes:

<< No. Provided that the crappy material is "diagosable" of something
 never before described, then it stays the type (holotype, actually).
 
 If the crappy material is later found not to have been diagnostic
 of a unique critter, then it ceases to be a valid taxon (provided
 that someone publishes this fact). The key is diagnosability,
 not completeness. >>

Species based on supposedly nondiagnostic material are usually known as
_nomina dubia_ (singular: _nomen dubium_). The names of such species remain
>valid<, however, in the sense that they cannot be reused for other species.
The best way to show that material is nondiagnostic is to exhibit two
different species to which the material is reasonably referable, such as, for
example, the type teeth of _Deinodon_, which are referable to either
_Gorgosaurus_ or _Dapletosaurus_. It is not sufficient to simply pronounce
material as being nondiagnostic to make it so; there is always the chance
that one is incompetent at arriving at a proper diagnosis, or has at least
not been sufficiently observant. It is also not sufficient to state that
material is nondiagnostic simply because it exhibits no autapomorphies, since
this condition itself may be diagnostic, of an ancestral species (for
example).

Type material is a "holotype" only if the original author unambiguously or
explicitly designated it to be the type, or it is the sole specimen on which
a species was originally based. Type material that is so designated by a
subsequent worker, as for example by selection from a type series, is called
a "lectotype."