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RE: What, if anything, is _Apatosaurus_ (Was: Ceratops (was RE: Pterosaur diversity (was: Re: Waimanu)))
Mike Taylor wrote:
Really? What are the criteria that you allude to exactly? That each
valid genus should be diagnosed by at least one autapomorphy? I would
think that most sauropod genera have that.
Probably most sauropods do have autapomorphies - but by no means all
(including some of those that are traditionally considered 'valid'). Like
Mickey, I think the requirement that each genus/species have at least one
autapomorphy in order to be deemed 'valid' is setting the bar way too high.
IMHO, having a unique *combination* of characters should be enough for a
diagnosis. I'm certain _Apatosaurus_ has this. For _Titanosaurus_, I think
this is a little trickier.
OK Mike, take a deep breath - I'm going to use a non-sauropod example. I've
heard that autapomorphies are hard to find in _Archaeopteryx_. But,
_Archaeopteryx_ is valid, right? It can be distinguished from every other
theropod taxon, just as _Apatosaurus_ can be distinguished from any other
sauropod taxon. Therefore, the validity of these genera is beyond reproach.
Rauhut (2004) upheld the validity of _Genyodectes_ based solely on a unique
combination of characters. It had not a single autapomorphy.
Mickey Mortimer wrote:
> This could be harder to prove. After all, unless an explicit etymology
is provided for each clade, > it is open to interpretation whether it is
named *after* a given genus. For example, we know
> that when Titanosauria was first named (was it by Bonaparte and Coria,
1993?) it was > ultimately named after _Titanosaurus_; but unless this is
explicitly stated in the paper, the > name could just be a descriptive term
in its own right ("titan lizards").
That's really stretching plausibility there.
Yes, it's called "plausible deniability". Everyone knows the truth, but no
one can prove it. :-)
I was really trying to illustrate the difficulties of *proving* that a
higher-level taxon is derived from a genus name.