Re: Yet even more questions (and I'm sure there'll be more...)

["Fam Jansma" <fam.jansma@worldonline.nl>]

>Hi everyone, it's me again to bother you with some questions...
>
:)
>
>1) Did Thescelosaurus have scutes on its body? I've seen many
>reconstructions with its flanks covered in armour, but I've also seen some
>without. Are the scutes on Thescelosaurus genuine or is it perhaps tan
>artifact of preservation (say, ankylosaur armour being deposited together
>with the thescelosaurus skeleton)
>
There was something about this in a book, can't remember the title anymore,
that it is not a real structure. The skin-remains do not show any sign of
armor, but are very rough in their texture. But this is based on a memory
and is hard to re-check since IDR the title anymore, it is also hardly
possible that Thescelosaurus, being an relatively late and advanced Hypsie,
was armored due to the fact that none of the Hypsies show any sign of armor.
The notion therefore of an armored Thescelosaurus can be biased on a
mis-interpretation of the material or a just a wild fantasy of the artists.
>
>2) Are heterodontosaurs basal ornithischians, basal ornithopods, or basal
>marginocephalians? Jamie A. Headden seems to think they're the possible
>ancestors of pachycephalosaurs, but others seem to place them as either
>basal Cerapoda or outside Cerapoda itself
>
Basal marginocephalians (called them Ornithopods in a pers.comm. to HP
Alessandro Marisa to give an overall impression...sorry), but this is what
he replied:

"(...) well I think that it's time to
re-evaluated the sistematic position of Heterodontosaurids as basal
Ornithopods, infact, there're evidence for which Heterodontosaurids must be
considered Marginocephalians. I also think that it's time to reconsidered
the diagnostic characters of Heterodontosaurids proposed by Weishampel and
Witmer (1990) expecially: (1) the presence of caniniform teeth in the
premaxilla and in the dentary: this teeth are present in Heterodontosaurids
(Heterodontosaurus, Lycorhinus and Abrictosaurus (UCL A.100) but are also
present in Pachycephalosaurs (Wannanosaurus, Goyocephale, Homalocephale,
Stegoceras and Prenocephale) in Neoceratopsids (Leptoceratops sp. (USNM
13863 (probably a new species of Leptoceratops)), Protoceratops,
Breviceratops and Bagaceratops) however, the caniniform teeth are absent in
all others Ornithischia. Moreover, the number of three premaxillary teeth is
present in Heterodontosaurids (Heterodontosaurus, Lycorhinus and
Abrictosaurus) but are present also in Pachycephalosaurs (Goyocephale,
Homalocephale, Stegoceras and Prenocephale) within Marginocephalians,
Neoceratopsids have a reduction to two premaxillary teeth, all others
Ornithischia when present the premaxillary teeth are in number of five, six,
or seven. (2) the chisel-shaped crowns of the cheek teeth with serrations
restricted to the uppermost third of the crowns of Heterodontosaurids is
also present in the basal Neoceratopsids Chaoyangsaurus youngi.
Others characters that linked Heterodontosaurids with Marginocephalians are:
(3) the lateral boss on the jugal, found in Heterodontosaurids,
Pachycephalosaurs and Neoceratopsids, however, within Marginocephalian
posses the derived condition of the jugal boss, infact, the jugal boss of
Heterodontosaurids and Pachycephalosaurs lacks the crests on the lateral
surface of the jugal (also present in Chaoyangsaurus youngi) present in the
Neoceratopsids, a jugal bos is also present in the Ornithopos Orodromeus and
Zephyrosaurus, but this could be explained as convergence. (4) the
premaxillary teeth of Heterodontosaurids (Heterodontosaurus),
Pachycephalosaurs (Goyocephale, Homalocephale, Stegoceras and Prenocephale),
and Neoceratopsids (Protoceratops and Breviceratops) progressively increase
in lenght from front to back, in others Ornithischia the premaxillary teeth
are subequal: (5) Heterodontosaurids posses a large diastema between the
premaxillary and maxillary teeth, this is present also in Pachycephalosaurs
and Neoceratopsids: (6) absence of an obturator process on the ischium found
in Heterodontosaurids, Pachycephalosaurs and Neoceratopsids: (7) presacral
count of 21-22 found in Heterodontosaurids, Pachycephalosaurs, and
Neoceratopsids in others Ornithischia the presacral count is at least 24:
(8) strap-shaped scapular blade found in Heterodontosaurids,
Pachycephalosaurs (Stegoceras UA-2) and Neoceratopsids (Protoceratops): (9)
distal expansion of the preacetabular process of the ilium found in
Heterodontosaurids (Heterodontosaurus), Stenopelix, Pachycephalosaurs
(Goyocephale, Stegoceras, and Homalocephale). About point (8) and (9)
interesting is the fact that Sereno in his chapter on Marginocephalian in
"Dinosaurs of Russia and Mongolia" use this two characters to link
Stenopelix with Pachycephalosaurs as a basal forms, well I've the suspect
(only the suspect) that Heterodontosaurids are more closely related to
Pachycephalosaurs than to Neoceratopsids."

But it is also mentioned in the Archives several times, although this is the
most recent mention of this alternative classification.
>
>3) Is there any evidence for mononykines, true Oviraptoridae or
>homalocephalid pachycephalosaurs in Late Cretaceous North America?
>
Mononykines:
Yes, three to be exact although these are based on isolated elements:
- "Ornithomimus" minutus (metatarsal)
- an pubis (was described in an issue of JVP)
- a metatarsal shown at the SVP

True Oviraptoridae:
No, at least, not that I know of

Homalocephalid pachycephalosaurs:
Yes, although undescribed. If you look on the Dinopress-website (is it still
on-line?) searching through the different issues, you will come to an
article about the Sue-site. Above the abstract there is a small picture of
some skull elements of a Pachycephalosaur and because it shows no sign of
being domed and that two holes in the roof for muscle attachement can be
seen (damn' names again...) is enough evidence for me that such an animal
was present in North America.
>
Cheers,

Rutger Jansma