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KEN'S ORNITHISCHIANS



Ken Kinman has once again attempted a classification of Ornithischia.  
Although I dislike his use of the word Ornithischiformes, paraphyletic
families, monotypic families, and the term "plesion;" it's much better than
some previous attempts :-)

now to comment:

Ken wrote:
<<One major change is a return to a more inclusive Family
Hypsilophodontidae---the paraphyly of that mess is better handled at generic
level, and I break that family down to show one possible topology (although
it remains very unsettled):>>

Well.... You're right.  Hypsilophodontoidae as traditionally conceived is
paraphyletic (and this is not a surprise to anyone really) and is pretty
messy.  There does seem to be a consistant pattern however.  

1) Agilisaurus is unofficially agreed to be one of the most basal
ornithopods, if it's even an ornithopod at all.

2) the North American forms Othnielia, Zephyrosaurus, Orodromeus, and
Thescelosaurus are more basal than Hypsilophodon (though not necisarily in a
monophyletic group.

3) Dryosaurus, Tenontosaurus, and Gaspirinisaura are basal Iguanodontians.

Additionally, my analyses consistantly demonstrate that Othnielia and
"Yandusaurus" form an exclusive clase, as do Orodromeus and Zephyrosaurus,
and that those two clades probably clade together as well.

<<10  Hypsilophodontidae
           1  Plesion "Y." multidens
           B  Othnielia (incl. Drinker)
           C  Zephyrosaurus
           D  Orodromeus>>

This group is possibly monophyletic, but it's monophyly is based on very few
characters.  Homoplasy is ever-present at the base of Ornithopoda.

<<           3  Parksosaurus
           ?  Gasparinisaura>>

Mickey's analysis joined these two based on a single synapomorphy which was a
reversal.  I am unaware of any other analyses which link these two.  
Additionally, these two, were they indeed in a monophyletic clade, would be
basal iguanodontians as demonstrated by Coria and Salgado.

<<           ?  Yandusaurus>>

See my recent dinolist posting on this animal.

<<           5  Tenontosaurus>>

Consistantly demonstrated to be a basal iguanodontian

<<The placements of Bugenasaura and Jeholosaurus are particularly
uncertain, and either of them could end up being moved higher in the
classification or down into Hypsilophodontidae.  >>

Jeholosaurus is probably at the base of the cerapod stem.  I would love to
see more data however and some good drawings and photos of the skull and
postcrania.  Bugenasaura IMHO is also close to the base of the cerapod stem,
but others think it is higher up in Ornithopoda.  I would like more remains
of this animal for sure.

<<The placement of Notohypsilophodon is very tentative (in Hypsil. clade
3, i.e., as a possible rhabdomorph).>>

Notohypsilophodon, despite the name, is not really that similar to
Hypsilophodon.  There are some features in the pretty fragmentary skeleton
that seem to suggest that it's kinda close to dryosaurids.  I am unconvinced
of Rhabdomorpha, and am similarly unconvinced of Muttaburrasauridae.  Aside
from being from South America, I cannot think of any possible synapomorphies
joining Notohypsilophodon with any of those guys.

<<       7  Plesion "T." dossi
       8  Tenontosaurus>>

Although the analysis that I ran including Jeholosaurus came up with this
result, I don't think it's correct.  T. dossi comes out as more basal than T.
tilletorum because of this single character: T dossi has a single set of
premaxillary teeth.  The analysis additionally was only skull data.  A full
analysis with postcranial data demonstrates that Tenontosaurus is probably
monophyletic.

Pete Buchholz
Tetanurae@aol.com