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Re: Could some chasmosaurs be hybirds?

On Thu, Sep 23, 2010 at 1:35 PM, Brad McFeeters
<archosauromorph2@hotmail.com> wrote:
> Something I find interesting about the new Sampson et al. chasmosaurine study 
> is that _Utahceratops_ and _Kosmoceratops_ are probably the most convincing 
> example so far of two seemingly distinct co-occuring ceratopsids that are 
> closely related in the same subfamily (This could also be the case for other 
> named taxa--_Chasmosaurus_ and _Mojoceratops_, _Triceratops_ and 
> _Torosaurus_--but it is complicated by competing views that lump these into 
> single taxa). ÂThe biogeographic analysis also suggests that chasmosaur taxa 
> were provincial, but lineages did cross over into the other province multiple 
> times during their evolution. Now, since the distinction between various 
> chasmosaurines was often merely ornamental, it is possible that some or all 
> of them were actually interfertile, and their evolutionary diversification 
> involved hybridization as well as traditional cladogenesis?
> Concerning _Vagaceratops_, for example, the cladistic analysis by Holmes et 
> al. found this taxon nested within _Chasmosaurus_, whereas that of Sampson et 
> al. found it to be the sister taxon of _Kosmoceratops_. ÂMaybe they're both 
> partly right- if the _Vagaceratops_ lineage was founded when _Kosmoceratops_ 
> or something like it wandered north and mated with the native population of 
> _Chasmosaurus_! ÂMaybe _Torosaurus_ and _Triceratops_ were usually distinct 
> populations, but there was still the rare occasional mating between them that 
> produced a _Nedoceratops_...
> I anticipate some DML readers will find this post uninteresting, because it 
> is not a very testable scientific hypothesis. ÂOr maybe you think it is. Â
> Anyway, I think it is fun to just speculate on things like this sometimes.

Perhaps it is testable. Here's a paper which uses morphological data
(as well as molecular data) to suggest that a certain mammalian
subspecies (Gorilla beringei graueri) is a hybrid population between
two species (G. gorilla and G. beringei):

The morphological data consists of dental oddities (supernumerary
teeth, etc.). These are probably not directly translateable to
ceratopsids, but perhaps there are other traits in archosaurs that
indicate hybridization?

T. Michael Keesey
Technical Consultant and Developer, Flex Specialist
Glendale, California