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About Varied / Hobbyist Member Zach A.Male/United States Recent Activity
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So, I finally decided to start a proper blog: palaeozoographer.wordpress.com…

So far, all I have is an introductory post, but I should be posting a series of posts on Dreadnoughtus in the next few days. Stay tuned!

-Zach

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Zach A.
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United States
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:icontraheripteryx:
Traheripteryx Featured By Owner Mar 1, 2015  Hobbyist General Artist
Dude, you have some cool skeletals! :D
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:iconfranz-josef73:
Franz-Josef73 Featured By Owner Sep 27, 2014  Hobbyist General Artist
Very nice skeletal work. Can't believe I missed your stuff for so long.
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:iconjuanh91:
JuanH91 Featured By Owner Sep 6, 2014
Hello,
Have you though about doing a GDI for Dreadnoughtus schrani? A lot of people think its weight is overestimated,
And I think you would be the perfect guy to do this, considering your previous works.

Best Regards
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Sep 6, 2014  Hobbyist General Artist
Yes, I am in progress of doing one. Hopefully it will be done by tomorrow. I agree that its mass is substantially overestimated. Watch this space.
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:icondarklord86:
darklord86 Featured By Owner Mar 4, 2014
I love your work!
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Mar 5, 2014  Hobbyist General Artist
Thank you!
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:icondarklord86:
darklord86 Featured By Owner Mar 5, 2014
No problem!
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:icontyrannosaurusprime:
TyrannosaurusPrime Featured By Owner Nov 26, 2013
Your thoughts on this? www.plosone.org/article/info%3…

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:iconpalaeozoologist:
palaeozoologist Featured By Owner Nov 28, 2013  Hobbyist General Artist
Well, I don't know much about morphometrics, so I don't really have any major thoughts. The only thing I will point out is that one of the methods they used in the study was UPGMA, which is a phenetics-based method. To quote Wikipedia, "In a phylogenetic context, UPGMA assumes a constant rate of evolution...and is not a well-regarded method for inferring relationships unless this assumption has been tested and justified for the data set being used." (en.wikipedia.org/wiki/UPGMA) The problem with phenetics is that it does not account for evolutionary relationships, and therefore is inferior to cladistics when trying to account for evolutionary relationships (see: en.wikipedia.org/wiki/Phenetic…. So it tells us that the Triceratops and Torosaurus specimens are morphologically distinct and cluster together (which we already knew), but I'm not sure what that means in regards to whether they are truly distinct species. So for instance, fig. 7 I believe is possibly misleading in this regard. It shows morphological distinctness, but what does this mean for ontogeny vs. species? This doesn't mean I think their study is wrong, it's just hard for me to tell if these methods are being appropriately used.

I would like to see a similar study on closely related living taxa that explicitly test ontogenic differences versus species differences  to test whether these methods are reliable. This may have already been done, but like I said, I don't know enough about it.

One thing that makes me wonder about this is deer. Deer are sexually dimporphic - (in general females don't have antlers, while males do have them) and on top of that, the antlers of male deers continually change as they get older (peramorphosis) (www.deerhunting.ws/skulls.jpg). If we took extremely close related species, but only used young adult specimens of one species, and old adult specimens of the other, could we reliably distinguish the species vs ontogenetic stages? My basic question is this: Can morphometrics reliably distinguish between ontogeny-related difference versus species related differences? I would need to see studies of this sort done on living animals (like deer, for example) for which we do know these differences already and see if they are matched by morphometric methods. Until I see that, it is difficult for me to know whether the study actually demonstrates what it says it demonstrates.

Ultimately, if Torosaurus and Triceratops truly are distinct, juvenile Torosaurus specimens that are clearly juvenile Torosaurus will be found.
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:icontyrannosaurusprime:
TyrannosaurusPrime Featured By Owner Dec 3, 2013
I see. Thanks. :)
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