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Re: New ankylosaur paper- Bissektipelta gen. nov.



Brad McFeeters wrote-

> Parish, Jolyon & Paul Barrett, 2004.  A reappraisal of the ornithischian
> dinosaur *Amtosaurus magnus* Kurzanov and Tumanova 1978, with comments on
> the status of *A. archibaldi* Averianov 2002.  Canadian Journal of Earth
> Sciences 41 (3): 299-306.
>
> Abstract: A fragmentary braincase from the Baynshirenskaya Svita
> (Cenomanian-Turonian) of Amtgay, Omnogov, People's Republic of Mongolia
was
> described as the holotype specimen of the ankylosaurid dinosaur,
*Amtosaurus
> magnus* Kurzanov and Tumanova 1978. However, the validity of this genus
has
> been questioned by several authors. Recently, a second species, based on a
> fragmentary specimen consisting of a braincase and partial skull roof, was
> assigned to *Amtosaurus* as *A. archibaldi* Averianov 2002. Here we
> re-assess the status of Amtosaurus and of the referred species, A.
> archibaldi. We conclude that "*Amtosaurus magnus*" is a nomen dubium that
> should be regarded as Ornithischia indeterminate. However, "*A*."
> *archibaldi* is a valid taxon, characterized by an autapomorphic feature
of
> the skull roof, and we refer this species to the new genus
*Bissektipelta*.

Eh, I'm not a fan of the method to determine validity or phylogenetic
placement this paper uses.  Basically, it says out of the characters
originally claimed to be autapomorphies of Amtosaurus, ankylosaurs A, B and
C have one, C, D and E have another, A, D and G have yet another, etc..  But
nowhere does it say one taxon besides Amtosaurus possesses all those
characters too.  I believe unique combinations of characters are just as
useful for supporting validity as completely unique autapomorphies.  It's
the same thing regarding its placement.  Of the supposedly ankylosaurian
characters originally listed for Amtosaurus, stegosaurs have one,
iguanodonts have another, pachycephalosaurs yet another.  But nowhere does
it list another clade with all of them.  Not that I know enough about
braincases or ornithischians to have an educated opinion as to what
Amtosaurus is, or if it really is valid, but this paper didn't convince me
it's a nomen dubium Ornithischia incertae sedis.  Also, what's with placing
the name Amtosaurus magnus in quotes, even if it was indeterminate?

Mickey Mortimer