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R: RE: Hypselospinus (Iguanodontia) from Early Cretaceous of Britain revised



The clade Rhabdomorpha was proposed by Pincemaille some years ago to encompass 
rhabdodontids, tenontosaurs, and Muttaburrasaurus.
 The analysis of Norman was focused on iguanodontians, so I don't blame him 
for excluding more basal taxa, however, it's premature at best to say what's 
going on with these purported 'ornithopods', at least until a comprehensive 
analysis will try to include all the jeholosaurs, thescelosaurids, 
rhabdomorphans, elasmarians, and the australasian taxa. Some of the supposed 
apomorphies of the new Hypsilophodontia have a wider distribution among 
ornithischians, so I would not be surprised if a new analysis with a more 
extensive taxon sampling will change things again. The new antarctic taxon 
presented at the SVP this year sound suspiciously like another elasmarian, 
although it should be noted that at least some orodromines (Koreanosaurus, 
Oryctodromeus) share some features with elasmarians, implying that our 
comprehension of the relationships of these taxa is just at its beginning. This 
is further exacerbated by a poor understading of the basal condition for 
ceratopsians and pachycephalosaurs (at least until Yinlong is fully described, 
and a jurassic pachycephalosaur is found...), and the lack of descriptive works 
for the Twin Mountain taxon, 'Gongbusaurus' wucaiwanensis, the skull of 
Othnielosaurus, and the new complete specimens of Tianyulong (intriguingly 
reminiscent of marginocephalians).
A number of specimens of Drinker is apparently known, but the whereabout of 
the material is unknown at present, and they're possibly lost.

The next few years will be very exiting for ornithischian workers.


>----Messaggio originale----
>Da: archosauromorph2@hotmail.com
>Data: 02/12/2014 2.43
>A: "dinosaur@usc.edu"<dinosaur@usc.edu>
>Ogg: RE: Hypselospinus (Iguanodontia) from Early Cretaceous of Britain 
revised
>
>> Date: Mon, 1 Dec 2014 09:01:15 -0800
>> From: bcreisler@gmail.com
>> To: dinosaur@usc.edu
>> Subject: Hypselospinus (Iguanodontia) from Early Cretaceous of Britain 
revised
>> 
>> for critical positions in the topology). This analysis suggests that
>> there is a fundamental split amongst the more derived (clypeodontan)
>> ornithopod ornithischians into the clades Hypsilophodontia and
>> Iguanodontia. There is evidence for anatomical parallelism and
>> convergence (homoplasy) particularly between large-bodied
>> representatives of both clades. 
>
>What Norman recovers here is a new version of Hypsilophodontia that includes 
Hypsilophodon, Tenontosaurus, and Rhabdodontidae. The tenontosaur-rhabdodontid 
clade was also recovered in the analysis presented by Karen Poole at SVP, but 
IIRC her poster had this clade moving "up" within Iguanodontia from its 
traditional position, closer to hadrosaurs than dryosaurs (the abstract isn't 
clear on this, so I'm just going on memory about that). So Norman's result is 
unique as far as I know, at least for modern cladistic analyses. Norman's text 
explains that thescelosaurids, jeholosaurids, Gasparinisaura, etc. are NOT 
hypsilophodontians, but instead are non-clypeodontan neornithischians. However, 
they are not actually included in the phylogenetic analysis, which uses 
Lesothosaurus as the only non-clypeodont. Clypeodonta is introduced as a new 
Infraorder (yes) of ornithopods, for the clade Hypsilophodon + Edmontosaurus.  
Notably absent from this paper is any mention of the ornithopods Anabisetia, 
Talenkauen, Macrogryphosaurus, Gideomantellia, or Trinisaura.  How might their 
inclusion affect Norman's "fundamental split" of clypeodonts?                   
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