Interesting study on Silesaurids

[Dynomikegojira]

https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0417

Hey everyone new member here I just wanted to know what's everyone thoughts on this study is.

[stargatedalek]

Is this why the recent Scelidosaurus paper cited Silesaurus as an ornithiscian?

[Dynomikegojira]

Was unaware of that honestly. Main thing I take of away from is if true rather than having little to no record of ornithischians in the Triassic it would be the exact opposite.

[Tyto_Theropod]

Interesting, but I wonder what evidence they provide for this conclusion?  Myself I feel it's best to wait for this to be discussed and see comments other authors have to say, and whether independent studies support the theory.

[Halichoeres]

First, welcome to the forum D @Dynomikegojira

I think this is an interesting hypothesis, and their data set as constructed seems to support it. I find the idea of a hiding-in-plain-sight set of basal ornithischians appealing, although it might just shift the difficulty to elsewhere in the tree, like the root of dinosaurs or of ornithodirans.

I was able to get the pdf, but not the supplement, but if the main phylogeny figure is anything to go by, their taxon sampling isn't really adequate to resolve the question of whether silesaurids are early ornithischians. I think a more distant archosaur than Euparkeria would be appropriate to root the tree, and if you're trying to work out Triassic ornithodiran relationships, there should probably be some pterosaurs in there as well. That said, hopefully having this hypothesis in the literature will mean that others trying to address this question in the future will sample those lineages and permit their model enough freedom to find this result again if the data support it.

One last nitpicky point: they call the silesaurids a stem group to the ornithischians, but the ornithischians by definition cannot have a stem because they're extinct and thus have no crown. Ornithischians and silesaurids are both part of the bird stem group regardless of whether this hypothesis holds up.

[Dynomikegojira]

Thanks so much I've always been slightly disappointed by the lack of Triassic ornithischians in fossil record so this study appeals to me but like you said a more comprehensive study is necessary for the bird line archosaurs.

[Sim]

I think it's most likely silesaurids are ornithischians.  Welcome to the forum D @Dynomikegojira!

[Dynomikegojira]

Thanks Sim glad to be here. One of the most amazings thing I take from this study is that if silesaurids are indeed ornithischians, the earliest members like Asilisaurus along with possible dinosaur Nyasaurus pushes back dinosaur divergence back to sometime in the Middle Triassic or even earlier based on the dinosaurmorph footprints at Świętokrzyskie Mountains.

[Tyto_Theropod]

An early, rapid diversification would certainly make sense given how many niches the Permian-Triassic Extinction Event (a.k.a. the Great Dying) would have left vacant.

[Pachyrhinosaurus]

Very interesting, indeed. There has been disagreement on whether atreipus tracks belong to silesaurs or primitive ornithischians, but I suppose now the answer could be both.