Comment on List of Biggest Dinosaurs by Paleo-King
Comment History
note, Tschopp, Maidment, & Giovarnardi (In press) found that "The consensus tree recovers the specimens of Apatosaurus louisae as more closely related to Brontosaurus excelsus than to A. ajax.". Makes sense, given the morphological dissimilarities between ajax & louisae compared to louisae & excelsus (link [it's on page 19]: drive.google.com/file/d/0B8Yj0…).
Apatosaurus:
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B. excelsus:
:origin()/pre11/aadb/th/pre/i/2015/126/8/5/_quot_thunder_lizard_quot__by_scotthartman-d1d9jek.jpg)
B. louisae:
:origin()/pre12/c524/th/pre/i/2015/114/1/5/the_real_thunder_lizard_by_scotthartman-d5aq6vk.jpg)
Apatosaurus:
B. excelsus:
B. louisae:
That's interesting; I missed that abstract! Cool that they're continuing with updating their matrix (though as Paleo-King has pointed out, they're not without flaws. I'm pretty sure that specimen level analysis will never singlehandedly sort out taxonomy).
To be honest, I'm not surprised that louisae belongs in Brontosaurus; I just didn't want to go ahead with that gut feeling without confirmation from the literature.
To be honest, I'm not surprised that louisae belongs in Brontosaurus; I just didn't want to go ahead with that gut feeling without confirmation from the literature.
lol true, though they seem to be better than most other analyses since they lack the bias of "this specimen definitely belongs to this genus" when in fact it belongs to a completely separate part of the family tree (looking at you Elaltitan...).
Well, that has pros and cons. A specimen-level analysis is highly likely to 'make up' clades based on ontogenetic, taphonomic, or individual variation, as well as being incapable of handling all available data in taxa known from disarticulated remains.
indeed, hence why I don't like to take even the best phylogenetic analyses as the be-all end-all of something's taxonomic affinities, ESPECIALLY if it's super incomplete.
I would argue that a phylogeny which has OTUs based on a solid alpha taxonomy is the best possible situation, and if the characters and analysis are good, while it might not be the be-all end-all, it's the best you've got for taxonomy. Of course, currently most phylogenies don't have a solid alpha taxonomy. To use Diplodocus as an example, the ideal situation would be to have two OTUs, respectively based exclusively on well-supported specimens of Diplodocus hallorum and Diplodocus carnegii (and coded unknown or polymorphic for characters which are variable, and doesn't include any character states resulting from juvenile anatomy) whereas Tschopp et al. treated all specimens as separate OTUs (allowing individual variation and ontogeny to affect the phylogeny) and most analyses just have Diplodocus (which probably includes a hodgepodge of indeterminate diplodocines, Galeamopus, and Kaatedocus).
"To use Diplodocus as an example, the ideal situation would be to have two OTUs, respectively based exclusively on well-supported specimens of Diplodocus hallorum and Diplodocus carnegii" IE a CM 84+94 OTU & a NMMNH P-3690+AMNH 223? (or USNM 10865) OTU.
Yes most phylogenies like to use composite OTU's, which seem to not last in the long run (Diplodocus spp, Apatosaurus spp, Omeisaurus spp, etc).
"allowing individual variation and ontogeny to affect the phylogeny" note they did attempt to take ontogeny into account, they have a whole section on it. And of course they attempted to take individual variation into it as well, hence why they did the character-based genericometer for separation (after all, if they hadn't taken individual variation into account every specimen which differed in more than two characters would've been a separate genus xDDD
Yes most phylogenies like to use composite OTU's, which seem to not last in the long run (Diplodocus spp, Apatosaurus spp, Omeisaurus spp, etc).
"allowing individual variation and ontogeny to affect the phylogeny" note they did attempt to take ontogeny into account, they have a whole section on it. And of course they attempted to take individual variation into it as well, hence why they did the character-based genericometer for separation (after all, if they hadn't taken individual variation into account every specimen which differed in more than two characters would've been a separate genus xDDD
They acknowledged both as considerations, but the simple fact of the matter is that they included those characters in the phylogenetic analysis and they affected results. For example, UW 15556 and BYU 1252-18531 claded together to the exclusion of the juvenile CM 566 because they were both adults, and the same is likely the reason why Giraffatitan brancai and Brachiosaurus altithorax claded to the exclusion of the juvenile Brachiosaurus SMA 0009. These are only the two most obvious cases where ontogeny affected results, but it is likely that they affected results in other, more subtle ways.