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Re: when is a Lazarus Taxon not a Lazarus Taxon?



Tim Williams writes:
>> Ladies and gentlemen, I give you: _Dravidosaurus_.  This Indian
>> form from the Coniacian seems to be a stegosaur (Yadagiri and
>> Ayyasami 1979, Galton and Upchurch 2004), contra Chatterjee and
>> Ruda 1996.  If that's correct, then it has a whopping
>> forty-million-year ghost lineage since the next-youngest known
>> stegosaur, _Regnosaurus_ from the Wealden (Hauterivian-Barremian)
>> of England (Sereno and Upchurch 1995).
> 
> _Wuerhosaurus_ may be younger than _Regnosaurus_, or at least
> coeval.  But you're right; if _Dravidosaurus_ is a stegosaur, that's
> a very long ghost lineage indeed.

The age of _Wuerhosaurus_ seems to be given, rather schizophenically,
as "Valanginian or Albian" in Galton and Upchurch 2004.  I leave it to
lovers of Chinese stratigraphy to sort that one out :-)

> However, although it's listed as a stegosaur by Galton and Upchurch
> (2004), I think this assignment is still questionable.

G&U seem pretty certain, but say that a redescription is needed.
Surprisingly, it is hardly mentioned at all in Maidment & Wei's (2006)
Chinese-stegosaur-fest.  (OK, they are concentrating on LJ Chinese
stegosaurs, but still.)

And in case you wondered, I have no opinion of my own :-)

> I was wondering if _Sonorasaurus_ might qualify as a Lazarus taxon,
> given (a) it is said to be of Cenomanian age (Carpenter and Tidwell,
> 2004); and (b) it is strikingly similar (identical?) to Late
> Jurassic _Brachiosaurus_ (Curtice, 2000) .

I've not seen the material so I'm hesitant to be too emphatic about
this; but since the sole _Sonorasaurus_ specimen ADSM-500 was
originally thought to be a hadrosaur (Thayer and Ratkevich 1995) and
then a Therizinosaur (Ratkevich's talk at DinoFest 1997), and since
the "nearly complete skull" turned out to be distorted dorsal, you
will forgive me if I am not quick to believe that the material can be
definitively identified as _Brachiosaurus_ :-)  It doesn't seem
unreasonable that it should be brachiosaurid, but since the EK was
crawling with putative brachiosaurids, or at least basal
titanosauriforms, that's not surprising.

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor    <mike@indexdata.com>    http://www.miketaylor.org.uk
)_v__/\  "What if everything is an illusion and nothing exists?  In that
         case, I definitely overpaid for my carpet" -- Woody Allen.