[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Phylogeny and evolutionary history of tyrannosauroid dinosaurs (free pdf)



This may be well known, but it was news to me that _Bagaraatan_ is a
chimera (based on specimens belonging to tyrannosauroids and other
taxa).

The Bayesian analysis recovers_Dryptosaurus_ as sister taxon to the
_Alioramus_/_Qianzhousaurus_ clade (which Mickey would call
_Alioramus_).  I find this fascinating, that _Dryptosaurus_ is a North
American alioramin (or if we want to get all technical re priority -
that _Alioramus_ and _Qianzhousaurus_ are East Asian dryptosaurins).
The same Bayesian analysis also has _Daspletosaurus_ as paraphyletic,
which (if upheld) would justify assigning the new species to a
separate (and new) genus.

Conspicuous by their absence is any mention of putative Australian
tyrannosauroids, including isolated pubic elements and the holotype
femur of _Timimus_ (Benson et al., 2010, 2012).  This is no surprise,
given that both referrals have proven controversial.


On Wed, Feb 3, 2016 at 8:56 PM, Mickey Mortimer
<mickey_mortimer111@msn.com> wrote:
> Great analysis, but inaccurate use of the term "nomen dubium" crops up again- 
> "We do not include the controversial taxon ‘Nanotyrannus lancensis’ in our 
> dataset, because our previous work has argued that this taxon is a nomen 
> dubium, as it is represented by material that belongs to juvenile 
> Tyrannosaurus rex."  No, that makes it a junior synonym.  A nomen dubium is a 
> taxon that is indeterminate, i.e. it cannot be distinguished from at least 
> two other taxa (e.g. ICZN Article 75.5).
>
> I have to congratulate Brusatte and Carr on including 58 pages of detailed 
> discussion on why they excluded certain characters used in Loewen et al.'s 
> tyrannosauroid analysis.  They also include characters from a "Carr and 
> Varricchio in press", which is no doubt the description of the Two Medicine 
> ?Daspletosaurus species, so it's nice to see that's so close to publiaction.  
> One thing that's odd is that the authors mention the Dueling Dinosaurs 
> specimen of 'Nanotyrannus' as one that "may hold the key to solving this 
> debate", but don't mention Jane at all.  Surely it would have been a good 
> opportunity for Carr to say he's working on a monograph of it.  I wonder if 
> Brusatte and Carr scored Raptorex as a juvenile, because its basal position 
> suggests not.  Finally, I wish people would just sink altai and 
> Qianzhousaurus already.  They're so similar to Alioramus remotus and at least 
> Carr has implied on his blog that altai only made it as a separate species 
> because other coauthors h
 ad
>   power in that decision.
>
> Mickey Mortimer
>
> ----------------------------------------
>> Date: Tue, 2 Feb 2016 07:46:49 -0800
>> From: bcreisler@gmail.com
>> To: dinosaur@usc.edu
>> Subject: Phylogeny and evolutionary history of tyrannosauroid dinosaurs 
>> (free pdf)
>>
>> Ben Creisler
>> bcreisler@gmail.com
>>
>> A new paper in open access:
>>
>> Stephen L. Brusatte & Thomas D. Carr (2016)
>> The phylogeny and evolutionary history of tyrannosauroid dinosaurs.
>> Scientific Reports 6, Article number: 20252 (2016)
>> doi:10.1038/srep20252
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.nature.com_articles_srep20252&d=CwIF-g&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=x82f3Wlkwtmbr1z8IAt9jA&m=8CS9pjkx3qV5CBLXTxRz9YaE6MYtepqCqNgBnjBu3tI&s=WOCZPY1s09-nD9bF8lCSpJKyyPc5GIH4VP3VPsitjJU&e=
>>
>> Tyrannosauroids—the group of carnivores including Tyrannosaurs rex—are
>> some of the most familiar dinosaurs of all. A surge of recent
>> discoveries has helped clarify some aspects of their evolution, but
>> competing phylogenetic hypotheses raise questions about their
>> relationships, biogeography, and fossil record quality. We present a
>> new phylogenetic dataset, which merges published datasets and
>> incorporates recently discovered taxa. We analyze it with parsimony
>> and, for the first time for a tyrannosauroid dataset, Bayesian
>> techniques. The parsimony and Bayesian results are highly congruent,
>> and provide a framework for interpreting the biogeography and
>> evolutionary history of tyrannosauroids. Our phylogenies illustrate
>> that the body plan of the colossal species evolved piecemeal, imply no
>> clear division between northern and southern species in western North
>> America as had been argued, and suggest that T. rex may have been an
>> Asian migrant to North America. Over-reliance on cranial shape
>> characters may explain why published parsimony studies have diverged
>> and filling three major gaps in the fossil record holds the most
>> promise for future work.
>