Ornithoscelida Rises: A New Family Tree for Dinosaurs

[Patrx]

Matthew Baron, David Norman and Paul Barrett argue that Saurischia may not be monophyletic!

Read Darren Naish's take on it here:
Ornithoscelida Rises: A New Family Tree for Dinosaurs.

[Minmiminime]

I've just seen this on the news! If they are correct, then this is MASSIVE. I mean, where do you even start?! Palaeontology is so exciting, and such a dynamic field these days

[suspsy]

This is certainly neat stuff, but it really shouldn't come as a huge shock. There's still a lot we don't know about dinosaurs.

A pity that so many books will be rendered obsolete!

[MLMjp]

OMG

This is BIG news.

This idea can be a game changer, and if the paleontologist community, after studying and revising this theory, conclude that this new idea is right and thus it should be accepted then this will cause a big mess in the community.

[Stuckasaurus (Dino Dad Reviews)]

Holy Jeebus, this is insane! The Saurischia-Ornithschia split has always seemed like one of the big bedrock dinosaur facts! In fact, it has always been so ingrained that people actually once seriously considered the idea that "dinosaur" wasn't even a proper scientific term, and that Saurischians and Ornithschians should be considered completely separate groups!

My initial takeaways from this are similar to Darren Naish's: first, this would make the feather distribution in dinosaur families make a little more sense, but secondly, and conversely, the lack of pneumaticity in the skeletons of "ornithischians" makes even less sense than it did before.

[Flaffy]

-mind blown-

[stargatedalek]

I was rather shocked at first glance, but re-reading it doesn't seem all that huge of a change (at least not as huge as it sounds). It's easy to describe this as a shuffling of the entire dinosaur family tree, but it really only moves sauropods and kin. We always knew "saurischians" and "ornithischians" shared a common ancestor, the only change is that we used to have sauropods and relatives as a sort of buffer between them.

This is however fairly big news for soft integument. It adds more validity to the idea that soft integument is an ancestral trait predating dinosaurs that was later adapted and lost through various groups.

[GasmaskMax]

I was rather shocked at first glance, but re-reading it doesn't seem all that huge of a change (at least not as huge as it sounds). It's easy to describe this as a shuffling of the entire dinosaur family tree, but it really only moves sauropods and kin. We always knew "saurischians" and "ornithischians" shared a common ancestor, the only change is that we used to have sauropods and relatives as a sort of buffer between them.

This is however fairly big news for soft integument. It adds more validity to the idea that soft integument is an ancestral trait predating dinosaurs that was later adapted and lost through various groups.

Potentially lost.

[Neosodon]

So Herrerasaurus is not a therapod? I've always thought that all carnivorous dinosaurs were therapods.

Ever since I was about 6 I classified all dinosaurs into these 6 main groups. 

Therapods
Sauropods
Stegosaurs
Ankylosaurs
Ornithapods
Ceratopsians

This classification has shaped the way I think about dinosaurs and even my collecting habits. It will be be difficult to get used to if a large portion of former therapods could no longer be classified as therapods.

[Faelrin]

Well there goes my childhood, haha. Well maybe. This is pretty interesting though, and I can't wait to delve into the details. This also means birds are finally considered "bird hipped" now and not "lizard hipped" anymore?

[stargatedalek]

I was rather shocked at first glance, but re-reading it doesn't seem all that huge of a change (at least not as huge as it sounds). It's easy to describe this as a shuffling of the entire dinosaur family tree, but it really only moves sauropods and kin. We always knew "saurischians" and "ornithischians" shared a common ancestor, the only change is that we used to have sauropods and relatives as a sort of buffer between them.

This is however fairly big news for soft integument. It adds more validity to the idea that soft integument is an ancestral trait predating dinosaurs that was later adapted and lost through various groups.

Potentially lost.

No, it can be said with genuine certainty several groups lost their soft integument.

So Herrerasaurus is not a therapod? I've always thought that all carnivorous dinosaurs were therapods.

I don't think Herrerasaurus was ever considered a theropod, instead I do believe it was at one time considered close to the ancestral condition for the whole of dinosaurs.

[CityRaptor]

If I remember correctly, even the postion of Herrerasauridae inside Saurischia was questioned at various points.

[Halichoeres]

If I remember correctly, even the postion of Herrerasauridae inside Saurischia was questioned at various points.

Yeah, some analyses had recovered it closer to the sauropodomorphs, which is reaffirmed here.

[Takama]

Does this mean we can cofidently  Reconstruct small Ornithopods like Hypsilophodon with feathers?


This shakes up my whole world.   I do not think i Will buy another Dinosaur book for a while now.

[Sim]

Personally, I don't find this convincing for a number of reasons.  I'll wait for several response papers before worrying too much about major changes in classification.  Additionally, in this study Eoraptor is suggested to be more closely related to Heterodontosaurus than to Panphagia, with Eoraptor and Heterodontosaurus being part of "Ornithoscelida" which Panphagia isn't a member of.  However, to me it seems Eoraptor is very similar to Panphagia, while Heterodontosaurus looks very different to these two.  In his Eoraptor skeletal, Scott Hartman even mentioned how similar Eoraptor is to Panphagia.

Panphagia: http://scotthartman.deviantart.com/art/All-Eater-213027613
Eoraptor: http://scotthartman.deviantart.com/art/Dawn-Thief-281226156
Heterodontosaurus: http://scotthartman.deviantart.com/art/A-mouth-full-of-different-teeth-363337739

I don't think Herrerasaurus was ever considered a theropod, instead I do believe it was at one time considered close to the ancestral condition for the whole of dinosaurs.

Herrerasaurus has been considered to be a theropod by palaeontologists and has been found to be one in some phylogenetic analyses.

[Halichoeres]

@Sim, I agree that patience is warranted, but I actually think this study was really well-executed. There was an infamous paper (also in Nature) that found that the closest relative of guinea pigs was rabbits, rather than other rodents, another mind-blowing finding. The Baron et al. study doesn't suffer from the same very poor taxon sampling as the "Guinea pigs aren't rodents" paper, and they present only their strict consensus tree, so I find it much more credible. There are no doubt technical aspects of dinosaur anatomy that I'm unfamiliar with that can be used to argue against the topology presented. However, I predict that some of the negative responses will rely on reasoning that optimizes a single favored character, which in the face of a study of this thoroughness constitutes special pleading.

[Neosodon]

Even if Hererasaurus was no longer considered a therapod it won't make much difference since the rest of the therapod family is descended from Ceolophysodae.

Does this mean we can cofidently  Reconstruct small Ornithopods like Hypsilophodon with feathers?


This shakes up my whole world.   I do not think i Will buy another Dinosaur book for a while now.

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.

[CrypticPrism]

All ornithodirans had an integumentary common ancestor.
I think this does mean chances for more feathering on ornithopods, though. And I've always loved quilly stegosaurs. Although I'm confused on the taxonomic placement of sauropods. Aren't they still closely related to theropods?

[Takama]

Neosodon are you forgeting about Kulindadromeous?

[CrypticPrism]

Neosodon are you forgeting about Kulindadromeous?

Probably. I have heard of  people saying that kulainodromeus didn't have feathers.