Ornithoscelida Rises: A New Family Tree for Dinosaurs

[Silvanusaurus]

Woah, you mean to say that our severely limited and indefinitely changing 'knowledge' about animals we know very little about, from many millions of years ago, might have been severely limited and changeable all along?
And there I was thinking that human science was the omniscient word of God.

[Cloud the Dinosaur King]

Yes, indeed. Btw, cloud, I love your channel.

Thank you.

No prob. We should probably get back on topic.

Anyways, can someone explain where sauropods fit?

I'm still confused about that too.

[Sim]

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

[Halichoeres]

Yes, indeed. Btw, cloud, I love your channel.

Thank you.

No prob. We should probably get back on topic.

Anyways, can someone explain where sauropods fit?

I'm still confused about that too.

If this new phylogenetic hypothesis is correct, then Saurischia (which used to include theropods, sauropods, and their closest relatives), would be restricted to the sauropodomorphs plus the herrerasaurids. That group would then be sister to all other dinosaurs (Ornithoscelida, which is all ornithischians plus all unequivocal theropods). Does that help?

[BlueKrono]

I always thought it strange that "bird-hipped" dinosaurs were the ones that DIDN'T evolve into birds. I agree with Sim though about basal sauropodomorphs and theropods.

[btb300]

Really interesting paper, but I think it is really nice to have these provocative researches, which challenge the accepted view from time to time. This is how science can really progress. Now I wouldn't be too concerned about the naming of the clades, that is just a play with words, and this example illsutates it pretty well that we tend to name things without knowing too much about them. As much as helping to comprehend the world around us it surely forces out brains to think in a certain framework, and does not allow to see us many things. It is also interesting to consider how difficult it must be to attribute anatomical similarities to either convergent evolution or philogenetic relationship based on often fragmentary, and of course very old fossil record.

[Cloud the Dinosaur King]

Yes, indeed. Btw, cloud, I love your channel.

Thank you.

No prob. We should probably get back on topic.

Anyways, can someone explain where sauropods fit?

I'm still confused about that too.

If this new phylogenetic hypothesis is correct, then Saurischia (which used to include theropods, sauropods, and their closest relatives), would be restricted to the sauropodomorphs plus the herrerasaurids. That group would then be sister to all other dinosaurs (Ornithoscelida, which is all ornithischians plus all unequivocal theropods). Does that help?

Yes. Thanks for that.

[CrypticPrism]

Thank good lord, someone explained it.
So this just means they're tied closer together?

[stargatedalek]

Thank good lord, someone explained it
So this just means they're tied closer together?

Yes, all it really does in terms of relations is remove sauropods as a buffer between theropods and ornithischians and place them closer to the origins of both groups (which to be fair has been suggested numerous times before). The only big changes proposed by this paper that others didn't is the coining of a new clade to accurately represent this change in literature.

[CrypticPrism]

Ah, I can see where all of the clutterjunk is coming from.

[Halichoeres]

Thank good lord, someone explained it
So this just means they're tied closer together?

Yes, all it really does in terms of relations is remove sauropods as a buffer between theropods and ornithischians and place them closer to the origins of both groups (which to be fair has been suggested numerous times before). The only big changes proposed by this paper that others didn't is the coining of a new clade to accurately represent this change in literature.

What do you mean by a buffer?

[stargatedalek]

Thank good lord, someone explained it
So this just means they're tied closer together?

Yes, all it really does in terms of relations is remove sauropods as a buffer between theropods and ornithischians and place them closer to the origins of both groups (which to be fair has been suggested numerous times before). The only big changes proposed by this paper that others didn't is the coining of a new clade to accurately represent this change in literature.

What do you mean by a buffer?

People generally don't (like to?) picture a common ancestor of theropods and "ornithischians". Instead a common ancestor of sauropodomorphs and ornithischians is what's generally conceived of. Sauropods are generally viewed as a group so incredibly different from either as to represent a disconnect between theropods and ornithischians.

[ZoPteryx]

Jeez, I go to the desert for a few days and when I get back the entire dinosaur family tree has been rewritten!?!? 

This is really interesting, though.  I'm not sure that I'm totally sold on the concept, but I've only been able to read the free supplemental material.*  Apparently one of their trees has a relatively low support value (< 75%), per comments on the DML.  That might be expected for this part of the tree, even good for all I know, but it seems insufficient given that the resultant conclusion is paradigm altering.  I eagerly await Andrea Cau and Mickey Mortimer's takes on the paper.  The best takeaway point would seem to be there's an extreme amount of plasticity around the base of the dinosaur family tree, more than previously realized, and only more fossils will be able to resolve it.  This raises all sorts of interesting questions regarding the distribution of skeletal pneumaticity, filamentous integument, and the relations of Chilesaurus and several other oddball taxa.  I'm still not sure how they reached their biogeographic conclusions either.

*Anyone have a copy of the paper they'd like to share?    Or will it be open access soon, I forget how Nature operates.

The authors redefine Dinosauria as the least inclusive clade including Passer + Triceratops + Diplodocus.

Ah, good to hear.  I was hoping that was addressed.  At least now dinosauria should be totally stable with regards to what are traditionally considered "dinosaurs" even if this topology is disproven.

[HD-man]

I eagerly await Andrea Cau and Mickey Mortimer's takes on the paper.

Me too. Both are consistently good sources of phylogenetic info.

[amargasaurus cazaui]

I  was able to get the actual paper...so probably best to message your email and I will send it to anyone who asks....no charge of course.

[Stuckasaurus (Dino Dad Reviews)]

I always thought it strange that "bird-hipped" dinosaurs were the ones that DIDN'T evolve into birds. I agree with Sim though about basal sauropodomorphs and theropods.

Even under this analysis, birds still come from a lineage of dinosaurs that are "lizard hipped" initially, and convergently evolve "bird hips" later.

[BlueKrono]

I always thought it strange that "bird-hipped" dinosaurs were the ones that DIDN'T evolve into birds. I agree with Sim though about basal sauropodomorphs and theropods.

Even under this analysis, birds still come from a lineage of dinosaurs that are "lizard hipped" initially, and convergently evolve "bird hips" later.

Interesting point. Convergent evolution for the win.

[Stuckasaurus (Dino Dad Reviews)]

No, only therapods have been found with feathers. Ornithapods are not descended from any therapod so it is still very unlikely even though they may be closer on the dinosaur family tree.

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.

[Neosodon]

No, only therapods have been found with feathers. Ornithapods are not descended from any therapod so it is still very unlikely even though they may be closer on the dinosaur family tree.

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.

I had not heard of Kulindadromeus or Tianyulong when I wrote that, so it was big shocker for me. Psittacosaurus is a different story though because it's body was still fully scaled and quills aren't the same as feathers. So I wouldn't go any further than saying some small Ornithapod dinosaurs had feathers.

[PaleoMatt]

o wow.