Ornithoscelida Rises: A New Family Tree for Dinosaurs

[Stuckasaurus (Dino Dad Reviews)]

There are several ornithopods now known to have possessed feathers. Kulindadromeus is the most famous, which really set the internet buzzing a little while ago, but Tianyulong and Psittacosaurus both possessed a row of feather-like quills along their backs.

No offense meant, but I have to make the following corrections.

1stly, last I checked, none of those dinos are ornithopods ("The fuzz of the heterodontosaurid Tianyulong...The many types of fuzz, bristlescales, and other projections on the neornithischian Kulindadromeus...The quills of the primitive ceratopsian Psittacosaurus": https://www.geol.umd.edu/~tholtz/G104/lectures/104dinorise.html ).

2ndly, last I checked, it's still not definite whether those dinos were feathered ("Note that the fuzz of the heterodontosaurid Tianyulong is very similar and some of the structures on Kulindadromeus are as well...Whether these turn out to be formed by convergence with theropods or retention in both groups of some ancestral dino-fuzz is not yet certain": https://www.geol.umd.edu/~tholtz/G104/lectures/104aves.html ).

Since we cannot do the facebook equivalent of a like here...I will go with...."Yes THIS" For my own thoughts the one closest seemingly to actual feathers might be Kulindadromeus.

Oops! I meant to say ornithischians. Anyway, I think it's splitting hairs (or dinofuzz) to say those aren't feathers. I'd be fine with referring to them simply as filaments, but they're definitely homologous to structures that would evolve into proper feathers in theropod dinosaurs.

[Sim]

I'm a bit skeptical I admit about the placing of herresaurs quite so far off from theropods, I'm inclined to think there's more than convergence going on there. But at the same time, is the placement of herrersaurs actually that important in this new tree? Wouldn't the same be accomplished by moving(/leaving) herrerasaurs closer to the ancestors of "ornithoscelida"?

It wouldn't be convergeance it would be primitiveness / plesiomorphy. Basal saurischians and basal ornithoscelidans should all look like theropods/herrerasaurs because all dinosaurs evolved from an ancestor who looked like that. The earliest ornithischians should look like theropods too, no matter where they are on the tree. Heterodontosaurids and Eocursor all look pretty theropod like.

And by the way, herrerasaurs were classified as early sauropodomorphs all the way back in the 80s. So the similarities the the sauropod branch have always been there. When I was a kid they were considered outside Dinosauria. Herrerasaurs being theropods was a brief short lived theory and was never very well supported. Bipedal meat eater is just the ancestral default state for all dinosaurs.

Based on what I've read, prior to this study, herrerasaurids being closer to sauropodomorphs than theropods hasn't been well supported, while herrerasaurids being theropods has been rather well supported, appearing to be among the most likely if not the most likely classification for them.  Similar to what you said in another thread, it's one hypothesis among several that is in need of further testing.  Just because the newest paper disagrees with a hypothesis doesn't mean the science is settled.

[Pachyrhinosaurus]

This reminds me of a few years back when that new paper came out re-classifying archaeopterygidae and (IIRC) putting deinonychosaurs in aves. It would be interesting if true but I'm hesitant to jump on board prematurely.

[HD-man]

I'm very surprised to see people now saying basal ornithischians look similar to theropods, as I don't see the similarity at all.  I'm even more surprised to see people suggesting basal theropods and basal sauropodomorphs look quite different.  I see a very strong similarity between them, with some being hard to tell whether they are a theropod or sauropodomorph!


Herrerasaurus: http://scotthartman.deviantart.com/art/Five-little-piggies-292594542
Tawa: http://scotthartman.deviantart.com/art/Tawa-the-perfect-intermediate-441064057
Coelophysis: http://scotthartman.deviantart.com/art/Coelophysis-bauri-581388929

Like Scott Hartman says in the description of his Tawa skeletal, Tawa appears to fill in the gap both morphologically and phylogenetically between herrerasaurids and coelophysids.


Another comparison, this time of three dinosaurs that lived at similar times, the Triassic ornithischian Pisanosaurus with Eoraptor and Panphagia.  I didn't do this as the initial comparison because of the incompleteness of Pisanosaurus's remains.

Pisanosaurus: http://scotthartman.deviantart.com/art/More-hypothetical-than-I-d-like-293551281
Eoraptor: http://scotthartman.deviantart.com/art/Dawn-Thief-281226156
Panphagia: http://scotthartman.deviantart.com/art/All-Eater-213027613

Even just based on its known remains, Pisanosaurus looks distinctly different to Eoraptor and Panphagia.  Eoraptor and Panphagia however look strikingly similar to each other.


Just my thoughts.  Also:

"I wouldn't start rewriting the textbooks just yet," says Steve Brusatte, from the University of Edinburgh. "This is just one analysis, and lots of recent studies recovered the more traditional grouping. Since this new result contradicts such a vast legacy of research, I think the bar [to accepting it] should be high."

From here: https://www.theatlantic.com/science/archive/2017/03/dinosaur-family-tree-saurischia-ornithischia-childhood-shattered-what-is-real-anymore/520338/

The new picture is "plausible, but not a slam-dunk," says Stephen Brusatte, a paleontologist at the University of Edinburgh, noting that the tree shuffle isn't based on new fossils, but on a new analysis of existing specimens. Researchers need to comb through the characters and evaluate the team's choices, he says. "It would be cool if they're right, [but] there's a big burden of proof when you're going against a long legacy in the literature." The authors haven't met that burden, says paleontologist Paul Sereno of the University of Chicago, because they don't explain how their analysis of traits altered the tree so dramatically.

From here: http://www.sciencemag.org/news/2017/03/t-rex-gets-new-home-shakeup-dino-family-tree

This post is worth re-posting.

[ZoPteryx]

^ Yeah, I'm still a little skeptical too.  Buriolestes really needs to be tested in their matrix.  Thankfully, I'm sure one of our fine friends at the Theropoda or the Theropod Database blogs will do so shortly.

I hadn't seen their articles about the study linked here yet, so here they are:

http://theropoda.blogspot.com/2017/03/ornithoscelida-20-saurischian-paraphyly.html
http://theropoda.blogspot.com/2017/03/la-tassonomia-dei-dinosauria-e-se.html

http://theropoddatabase.blogspot.com/2017/03/ornithoscelida-lives.html

^ Be sure to read the comments in those as well.  I think the main thing we can all agree on is the new definitions suggested in this paper are poor, even if the clades they represent are accurate.

[Stuckasaurus (Dino Dad Reviews)]

This reminds me of a few years back when that new paper came out re-classifying archaeopterygidae and (IIRC) putting deinonychosaurs in aves. It would be interesting if true but I'm hesitant to jump on board prematurely.

Whatever happened with that study, anyway? Most people obviously have not gone along with it, but I don't remember actually hearing of any formal rebuttal.

[ZoPteryx]

This reminds me of a few years back when that new paper came out re-classifying archaeopterygidae and (IIRC) putting deinonychosaurs in aves. It would be interesting if true but I'm hesitant to jump on board prematurely.

Whatever happened with that study, anyway? Most people obviously have not gone along with it, but I don't remember actually hearing of any formal rebuttal.

I vaguely remember something like that.  Wasn't it a BANDit study? If so, that would explain why everyone just elected to ignore it.

[Dinoguy2]

This reminds me of a few years back when that new paper came out re-classifying archaeopterygidae and (IIRC) putting deinonychosaurs in aves. It would be interesting if true but I'm hesitant to jump on board prematurely.

Whatever happened with that study, anyway? Most people obviously have not gone along with it, but I don't remember actually hearing of any formal rebuttal.

I vaguely remember something like that.  Wasn't it a BANDit study? If so, that would explain why everyone just elected to ignore it.

No it wasn't a bandit study, and it didn't put deinonychosaurs in Aves - just like this paper, they re-defined Aves to keep them out. But the same result hasn't been replicated by better datasets. Not that it might be true or not - Archaeopteryx has features of birds, troodonts, and dromies, so it could realistically be impossible to ever know which branch it's really on. Expect studies finding it moved from one to another pretty much forever. Anchiornis and Aurornis have bounced around a lot more.

[ZoPteryx]

Uh-oh, potentially the first nail in ornithoscelida's coffin: sloppy coding

http://theropoddatabase.blogspot.com/2017/03/ornithoscelida-tested-adding-taxa-and.html

[Tyto_Theropod]

Much like many people here, I'm enthusiastic about this and i think it's plausible, but that it needs to be reviewed for potential problems before we go around declaring Ornithoscelida as a thing. Myself I can see arguments for both interpretations.

[HD-man]

Uh-oh, potentially the first nail in ornithoscelida's coffin: sloppy coding

http://theropoddatabase.blogspot.com/2017/03/ornithoscelida-tested-adding-taxa-and.html

I hope they publish in PeerJ like they've been talking about in the comment section.

[ZoPteryx]

Uh-oh, potentially the first nail in ornithoscelida's coffin: sloppy coding

http://theropoddatabase.blogspot.com/2017/03/ornithoscelida-tested-adding-taxa-and.html

I hope they publish in PeerJ like they've been talking about in the comment section.

Yeah, me too.  If ornithoscelida can survive their testing, it can survive anything! 

[CrypticPrism]

The good thing is fluffy ornithischians , the sad thing is scaly herrerasaurids.

[ZoPteryx]

The good thing is fluffy ornithischians , the sad thing is scaly herrerasaurids.

Maybe, maybe not.  Given the current lack of evidence, it could still go either way. 

[Silvanusaurus]

The good thing is fluffy ornithischians , the sad thing is scaly herrerasaurids.

Why would this be sad? Animals are what they are.

[Sim]

The good thing is fluffy ornithischians , the sad thing is scaly herrerasaurids.

Why would this be sad? Animals are what they are.

Well said, Silvanusaurus.

[stargatedalek]

The good thing is fluffy ornithischians , the sad thing is scaly herrerasaurids.

Well this is further evidence that dinosaur integument shares a direct ancestor with pterosaurs and crocodiles, so herrersaurids being closer to this ancestor certainly could have had soft integument, just not true feathers.

[CrypticPrism]

Oh. Well, it then means no one can call me a "feathernazi".

[Sim]

Uh-oh, potentially the first nail in ornithoscelida's coffin: sloppy coding

http://theropoddatabase.blogspot.com/2017/03/ornithoscelida-tested-adding-taxa-and.html

Wow...  Also, this seems to confirm some things I had been thinking:

1. Some of the suggested shared features are actually examples of convergence.

2. When more species are added / corrections are made, some of the results of the phylogentic tree change.  This is why I'm sceptical about major classification changes unless there's clear evidence for it.  Especially for groups that are known for having an unstable position in the family tree like Eoraptor and herrerasaurids.


There are some things I appreciate about the Baron et al. study though.

1. It's made me think about and learn more about fascinating basal dinosaurs.

2. Based on some recent reading I did, it appears ranked taxonomy has largely fallen out of favour among dinosaur palaeontologists, although some have continued to use this form of classification (sometimes disagreeing on what a group's rank should be though).  Personally, I've been feeling some groups being suggested to have the same rank doesn't seem right at all.  For example Theropoda, Ankylosauria and Stegosauria have all been considered suborders.  The level of diversity in both Ankylosauria and Stegosauria is SO much lower than in Theropoda though, even if one excludes non-Mesozoic species.  Even if Thyreophora was considered to be at the same rank as Theropoda, the diversity among Mesozoic theropods is still so much higher than in Thyreophora.  So what's the point of putting Ankylosauria and Stegosauria at the same rank as Theropoda?  I can say the same for all the other ornithischian suborders.  It might just be me, but it feels like these ranks tend to misrepresent the diversity present in the group.
I'm actually liking considering Theropoda to be equivalent to Ornithischia.  Both groups appear in the fossil record at a similar time, and both seem to have a similar level of diversity during the Mesozoic.

[Halichoeres]

@Sim: Not just paleontologists, although they've arguably led the charge. I agree that the traditional suborders don't make a ton of sense. I try to avoid using ranks when I can, though it's difficult to avoid in extant taxa where established ranks are upheld mostly by tradition. I think the fact that taxonomies that include a lot of fossil organisms are more prone to disruption by new discoveries, it was easier to discard artificial ranks in paleontology.