Re: Miragaia paper online

[Tim Williams <tijawi@yahoo.com>]

[Sorry for inundating the list with stegosaur messages.  This is my last for 
the day, I promise.  I had meant to sent this one out earlier, but it was 
overtaken by other replies...]


Thomas R. Holtz, Jr. <tholtz@umd.edu> wrote:


> OctÃvio Mateus, Susannah C.R Maidment & Nicolai A
> Christiansen
> A new long-necked âsauropod-mimicâ stegosaur and the
> evolution of the plated
> dinosaurs
> Proc. R. Soc. B published online before print February 25,
> 2009,
> doi:10.1098/rspb.2008.1909


Mateus &c suggest that the increased number of cervicals (to 17!) in _Miragaia_ 
could have either come about by cervicalization of the anterior dorsals; 
insertions of new vertebrae to the cervical series; or both.  The first 
hypothesis (recruitment of pre-existing dorsals into the cervical series) would 
lead to fewer dorsals (as Mateus &c mention).  Strangely conspicuous by its 
absence from the paper (especially in Table 1) is  _Wuerhosaurus ordosensis_.  
According to the original description (Dong, 1993), _W. ordosensis_ has 11 
dorsal vertebrae, "the lowest number of dorsals known in any stegosaur" (which 
remains true today, AFAIK).  If this is the result of the anterior dorsals 
being 'cervicalized', this would give _W. ordosensis_ a neck that was composed 
of around 15 cervicals.  That's less than _Miragaia_, but more than other 
stegosaurs.

Maidment et al. (2008) referred _W. homheni_ (the type species) to 
_Stegosaurus_, and regarded _W. ordosensis_ as a nomen dubium.  But the latter 
may be worth a second look.

Refs

Dong Z._M. (1993) A new species of stegosaur (Dinosauria) from the. Ordos 
Basin, Inner Mongolia, Peopleâs Republic of China.  Canadian Journal of Earth 
Sciences 30: 2174â2176.

Maidment, S.C.R., Norman, D.B., Barrett, P.M., and Upchurch, P. (2008) 
Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia).  Journal 
of Systematic Palaeontology 6: 367-407.




Cheers

Tim