Caseosaurus, Herrerasaurus--dinosaurs or not?

[Halichoeres]

Here's something fun! This study reexamines Caseosaurus and finds it to be part of the sister group of Dinosauria, along with Herrerasaurus. So the hypothesis here is that Herrerasaurus isn't a dinosaur at all, and that Dinosauria consists of Ornithoscelida + Sauropodomorpha. Another piece of the public debate about WHAT EVEN IS A DINOSAUR

Open access: http://www.app.pan.pl/article/item/app003722017.html

[Sim]

As soon as I saw Matthew Baron was one of the authors, I thought this would probably not be much more than another paper to support Ornithoscelida.  It looks like that thought was right.

It's good to see some important species added to their dataset that were missing in their previous pro-Ornithoscelida papers.  However, adding these species results in significant changes to the positions of some of the most basal species that were already in the dataset, and this reinforces my thought that their positions in the phylogenetic analysis don't actually mean much and it's not clear where they should group.  After all, there are still some important gaps near the base of Dinosauria, who knows what will happen if some of these 'missing species' are discovered and included in a phylogentic analysis.  Especially important is that it's been suggested Pisanosaurus is not actually an ornithischian or a dinosaur, and if this is correct are any Triassic ornithischians known?  What could it mean if the only know ornithischians are from the Jurassic onwards, while Triassic theropods and sauropodomorphs are known?

I think it would be good to have a paper regarding the possible validity of Ornithoscelida that doesn't have any member of the Ornithoscelida team as authors.  While it makes sense for the Ornithoscelida team to publish papers about it, as far as I'm aware all three of the pro-Ornithoscelida papers have had Matthew Baron as an author, and two also had Paul Barrett as an author.  So the support for Ornithoscelida is each time coming from mostly the same people.  I'm already quite sceptical about a lot of the results that have come from these Ornithoscelida papers.  What would make things they suggest more convincing would be if palaeontologists who are independent of the Ornithoscelida team also find support for their results.  At the moment it seems to just be Matthew Baron + (other name(s)) saying why one should believe in Ornithoscelida.

So the hypothesis here is that Herrerasaurus isn't a dinosaur at all, and that Dinosauria consists of Ornithoscelida + Sauropodomorpha.

Herrerasaurids are known for having an unstable position in phylogenetic analyses, so I'm not surprised this new one finds them outside of Dinosauria, especially since this one places them just outside of Dinosauria.  This means if Dinosauria were made to be slightly more inclusive, including just the next most closely related group, herrerasaurids would be within Dinosauria.  Personally, I still see what appears to be a noticeable evolutionary transition from a Herrerasaurus-type animal to a Tawa-type animal to a Coelophysis-type animal, which I find supports the idea these are all theropods.  And I still think Eoraptor is most likely a sauropodomorph, which is supported by the similarity between it and Panphagia.

[stargatedalek]

Especially important is that it's been suggested Pisanosaurus is not actually an ornithischian or a dinosaur, and if this is correct are any Triassic ornithischians known?  What could it mean if the only know ornithischians are from the Jurassic onwards, while Triassic theropods and sauropodomorphs are known?

That is evidence in very strong favour of Ornithoscelida. With all of the discussion around Ornithoscelida it's easy to forget that Herrerasaurids weren't actually moved, just re-labeled, and this paper seems to be expanding on that same concept.

Ornithischians were moved, placed as a descended splinter group to theropods rather than a sister group. This makes it look like Sauropods and Herrersaurs were moved further from traditional Theropods but it actually follows a very standard placement for Herrersaurids and Sauropods.

[Sim]

This new paper still considers Pisanosaurus an ornithischian though.   I wonder what would happen if it were included as a silesaurid instead?

[ZoPteryx]

I share Sim's caution on the matter.  One thing that makes me cautious other than the authorship is the lack of resolution in the cladogram among dinosauria.  Ornithischia is decent, but theropods and sauropodomorphs aren't well resolved at all.  Neither are herrerasaurs in their new position, which are in a polytomy with Saltopus, which is clearly not similar enough warrant that position.  Sister-taxa sure, but polytomy?!  All this leads me to think their character sampling for dinosaurs just isn't that good.

Thankfully, Mickey Mortimer and co apparently have a rebuttal of sorts in review.  I really don't care whether ornithoscelida turns out to be valid or not, I just want whatever the result is to be well supported by a proper analysis.

[Sim]

All this leads me to think their character sampling for dinosaurs just isn't that good.

One of the main criticisms of their results before was poor character sampling.  I share your concern that their character sampling still isn't good, and that this could be affecting the results.

I've remembered there has been one other paper regarding the possible validity of Ornithoscelida, which found that correcting miscodings in the Ornithoscelida paper resulted in theropods being closer to sauropodomorphs than ornithischians: http://dml.cmnh.org/2017Nov/msg00002.html  As can be seen in the link, the Ornithoscelida paper authors also responded.  Both in Langer et al.'s paper, and Baron et al.'s response, some of the most basal species get changed placements in the family tree.  For example Baron et al. find Daemonosaurus to be an ornithischian there, but a little over two months later Daemonosaurus is found to be a theropod in Baron's new paper (the topic of this thread).  This is the kind of thing I mean about how certain changes in place on the family tree don't mean much.


Mickey Mortimer and co's paper looks like it will be helpful.  Quoting Mickey:

For the Ornithoscelida project, my team (Cau, Gardner, Deccechi and Marjanovic) and I basically have to provide references for some scores (which I'm responsible for as I did the scoring, and so am the one causing the holdup), complete the bibliography and finish the conclusions.  And create figures.  I was briefly disheartened by the publication of Langer et al. (2017), but our paper is so much more extensive and explicit that I feel it will significantly add to the conversation, and Langer et al. messed up quite a bit too.  For instance, remember how Baron et al. (2017) scored 30 taxa that lack preserved integument as lacking filaments?  Langer et al. only changed nine of those scores to unknown despite perhaps being the most obvious error in the matrix.  We detail some of their errors in the paper as well.

From here: http://theropoddatabase.blogspot.co.uk/2017/12/happy-new-years-and-sorry-for-hiatus.html

The parts in bold in the quote above seem so bad...

[Halichoeres]

Ha, I didn't look at those character codings. Hilarious. It can be hard to sample some of these specimens when people get proprietary with them and sit on them for years. How long did Eoraptor languish without any real progress being made on its study?

[Dinoguy2]

As soon as I saw Matthew Baron was one of the authors, I thought this would probably not be much more than another paper to support Ornithoscelida.  It looks like that thought was right.

It's good to see some important species added to their dataset that were missing in their previous pro-Ornithoscelida papers.  However, adding these species results in significant changes to the positions of some of the most basal species that were already in the dataset, and this reinforces my thought that their positions in the phylogenetic analysis don't actually mean much and it's not clear where they should group.  After all, there are still some important gaps near the base of Dinosauria, who knows what will happen if some of these 'missing species' are discovered and included in a phylogentic analysis.  Especially important is that it's been suggested Pisanosaurus is not actually an ornithischian or a dinosaur, and if this is correct are any Triassic ornithischians known?  What could it mean if the only know ornithischians are from the Jurassic onwards, while Triassic theropods and sauropodomorphs are known?

I think it would be good to have a paper regarding the possible validity of Ornithoscelida that doesn't have any member of the Ornithoscelida team as authors.  While it makes sense for the Ornithoscelida team to publish papers about it, as far as I'm aware all three of the pro-Ornithoscelida papers have had Matthew Baron as an author, and two also had Paul Barrett as an author.  So the support for Ornithoscelida is each time coming from mostly the same people.  I'm already quite sceptical about a lot of the results that have come from these Ornithoscelida papers.  What would make things they suggest more convincing would be if palaeontologists who are independent of the Ornithoscelida team also find support for their results.  At the moment it seems to just be Matthew Baron + (other name(s)) saying why one should believe in Ornithoscelida.

So the hypothesis here is that Herrerasaurus isn't a dinosaur at all, and that Dinosauria consists of Ornithoscelida + Sauropodomorpha.

Herrerasaurids are known for having an unstable position in phylogenetic analyses, so I'm not surprised this new one finds them outside of Dinosauria, especially since this one places them just outside of Dinosauria.  This means if Dinosauria were made to be slightly more inclusive, including just the next most closely related group, herrerasaurids would be within Dinosauria.  Personally, I still see what appears to be a noticeable evolutionary transition from a Herrerasaurus-type animal to a Tawa-type animal to a Coelophysis-type animal, which I find supports the idea these are all theropods.  And I still think Eoraptor is most likely a sauropodomorph, which is supported by the similarity between it and Panphagia.

I thought the same thing, but Andrea Cau posted a test of his own on Facebook that found the same result of non-dinosaurian herrerasaurs. It also found Ornithoscelida, but wasn't testing for it so that's irrelevant. Keep in mind Ornithoscelida and non-dinosaur herrerasaurs are two separate hypotheses and one could be right if the other isn't. Interestingly, Cau found Daemonosaurus to be a herrerasaur.

But it's certainly making me nostalgic for the early '90s!