Reevaluating Chilesaurus

[suspsy]

Turns out this little herbivore may be one of the most important transitional fossils in the long history of evolution!

http://www.bbc.com/news/science-environment-40890714

[Neosodon]

I've always been interested in finding out more about the first herbivorous dinosaurs since little seems to be known about them. But what's with the only 2 fingers? I'd like to hear that explained.

[PaleoMatt]

Does this add even more credibility to the new family tree hypthesis?

[Flaffy]

I've always thought that there was more to this little guy, unfortunately Yi Qi took the spotlight.

[ceratopsian]

Does this add even more credibility to the new family tree hypthesis?

That is my understanding.  The article itself is short and not hidden behind a paywall, so worth a look.

I was thrown when I saw a brief newspaper article this morning by Chilesaurus being late Jurassic in age.  But of course the hypothesis is that there is a lengthy ghost lineage lurking behind it.

[stargatedalek]

Nice to see this finally being published, was among the people saying it was probably a basal ornithopod and not sauropod from the beginning.

[Sim]

Andrea Cau wrote a good blog post about this: http://theropoda.blogspot.co.uk/2017/08/chilesaurus-e-un-ornithischio-in.html

The authors of this new study that finds Chilesaurus to be an ornithischian are two of the authors of the recent Ornithoscelida hypothesis, and like in that earlier study there are still important basal dinosaurs that have not been included in the analysis!  Even worse is that Chilesaurus has initially been found to be a tetanuran with some ornithischian-like features, and this new analysis doesn't include any (other) tetanurans!  So of course Chilesaurus is going to be found to be an ornithischian, since none of the theropods it's like have been included, so it will end up appearing closer to other animals it's like, in this case ornithischians.  This is just absurd...  As Andrea Cau said, if you want to show Chilesaurus is an ornithischian, you have to include all the other possibilities, especially tetanurans.  Without tetanurans, the analysis is inadequate at showing what it claims.

In the BBC article, it looks like the Papo running T. rex is used for the silhouette in the dinosaur family tree image.

[ceratopsian]

......  this new analysis doesn't include any (other) tetanurans!  So of course Chilesaurus is going to be found to be an ornithischian, since none of the theropods it's like have been included, so it will end up appearing closer to other animals it's like, in this case ornithischians.  This is just absurd...  As Andrea Cau said, if you want to show Chilesaurus is an ornithischian, you have to include all the other possibilities, especially tetanurans.  Without tetanurans, the analysis is inadequate at showing what it claims.

Is it true that they didn't include any tetanurans?  In their dataset, they list genera like Cryolophosaurus and Sinosaurus.  Aren't they within Tetanurae?  But I'm not a scientist, so might misunderstand here.

[Sim]

That's a good point, ceratopsian, as Cryolophosaurus and Sinosaurus have been found to be tetanurans at times.  However, they might not be tetanurans, for example in the current Theropod Database phylogeny they are found outside Tetanurae and tentatively within Dilophosauridae: http://theropoddatabase.com/Phylogeny%20of%20Taxa.html

[ceratopsian]

Thank you Sim, that's a good resource to which you've given the link.

[ZoPteryx]

Hmm, not sure I'm quite buying this or the Ornithoscelida hypothesis at this point, not without a better matrix at least.