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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):
http://onlinelibrary.wiley.com/doi/10.1111/j.1558-5646.2009.00858.x/full

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
http://tmkeesey.net/