[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

JEHOLOSAURUS



Mickey Mortimer writes (about _Jeholosaurus_):
<<Six teeth extend the length of the premaxilla, so that not even the most
anterior part is edentulous.  This is the same number as Lesothosaurus, but
the latter condition is more basal than even that taxon, though Bugenasaura
and Agilisaurus exhibit it.>>


No ornithischian has premaxillary teeth going to the very tip of the
premaxilla.  The published images of Jeholosaurus exhibit a condition that's
very similar to the non-reconstructed skulls of Lesothosaurus, Bugenasaura,
and Agilisaurus, as well as Huayangosaurus- premaxillary teeth running the
whole length of the bone without an edentulous portion at the tip of the
snout, as in "hypsilophodontids" and heterodontosaurids.

<<The deeply inset ventral margin suggests cheeks may have been present, if
they were in any ornithischian.>>


They were, see:

http://www.cmnh.org/fun/dinosaur-archive/2001Feb/msg00327.html
http://www.cmnh.org/fun/dinosaur-archive/2001Feb/msg00381.html
http://www.cmnh.org/fun/dinosaur-archive/2001Feb/msg00770.html

<<The figures make it look like there are paired nasal fossae separated by
the midline, so I am uncertain about this.  A midline nasal fossa may also
be present in Agilisaurus and "Yandusaurus" multidens.>>


I believe that this is really the result of liberal shading on the parts of
the illustrators used by He et Cai and Peng in the descriptions of "Y"
multidens and Agilisaurus.  Photos I have seen of these animals do not really
show and sort of nasal fossae.

Additionally, the truely bizarre paired nasal fossae of Jeholosaurus only
appears to be present in the second, probably juvenile skull.  What this is,
and of what phylogenetic significance it is, I don't know.  I really wish
that the description were more complete, with photos of the bones, and at the
very least drawings of the postcrania.

<<No palpebrals are preserved.>>

This is truely bizzare as well.  Additionally, the caudal portion of the
frontals appear to remove most of the postorbital bones from contact with the
orbit itself, which as far as I know is unique among ornithischians.  There
are no images of either skull in dorsal view, so it's unknown if the frontals
were as thin as in most basal ornithischians, or if they'd convergently
widened, as it appears they might have.

This animal is probably pretty basal on the ornithischian tree, and probabaly
is not even an ornithopod as far as I'm concerned
.  As for where I think it
goes specifically?  Well, you'll have to wait til I revamp my character
matrix and enter this thing in...  It would help a lot though if I had some
postcranial characters to use, but we'll just have to wait and put it in the
"skulls only" matrix.

All in all, this is a eally important animal and I look forward to seeing
much more of it.

Pete Buchholz
Tetanurae@aol.com