Re: Two Questions

["Mickey Mortimer" <Mickey_Mortimer111@msn.com>]

Jaime Headden wrote-

> The skull, despite it's small "ceratosaurian" appearance, is
> not well-preserved and has been only poorly described. Laying in state in
> the IVPP vertebrate paleontology collection (IVPP V), the material needs a
> good spanking in the description department.

I completely agree.

>   However, many reasons to consider this animal to be non-dinosaurian
> involve the presence of many non-dinosaurian or basal dinosaur conditions,
> including suborbital maxillary tooth row, no ventral extent of the
> antorbital fossa, rostral lachrymal protuberances, and an oddly-shaped
> orbit with a ventral "notch" and posterior process of the lachrymal that
> projects into the orbit and may form a platform for a palpedral
> ossification. External nares very dorsally positioned, not rostrally, and
> well posterior to the rostral limit of the premaxilla.

While I agree there is a strong possibility Lukousaurus is non-dinosaurian,
these characters are not very good evidence in my opinion.  The suborbital
maxillary toothrow is found in non-tetanurines, the antorbital fossa is
similarily non-extensive in Herrerasaurus and abelisaurids, the lacrimal
horns are typical of post-herrerasaurid theropods.  I think the "posterior
lacrimal process" may be an artifact caused by a portion of the lacrimal
above being broken off.  My favorite non-dinosaurian interpretation is
sphenosuchian, but it could also be an abelisauroid.  See
http://www.cmnh.org/fun/dinosaur-archive/2000Sep/msg00086.html for more
details.

Mickey Mortimer