New Eotyrannus Description

[Concavenator]

Darren Naish announced 2 days ago the publication of a new description of Eotyrannus lengi (with Andrea Cau as a coauthor) he's been working on for a very long time.

From Twitter: https://twitter.com/TetZoo/status/1545128379116126208

A summary/thoughts post by Darren Naish on his blog.

Here's the paper.

And here's the new skeletal:



The phylogenetic analysis featured in the paper sheds some interesting results...

- There's no such thing as Stokesosauridae (in which Eotyrannus was nested before).
- Yutyrannus outside of Proceratosauridae.
- Chilantaisaurus is recovered as a Tyrannosauroidea.
- Megaraptoridae were already suspected to be coelurosaurs (and tyrannosauroids) before and this new paper reaffirms it.
- Teratophoneus outside of Tyrannosauridae! (and Bistahieversor too, although IIRC this was already known)

A quick read at his blog entry and I learnt this species' description was preliminary, as suggested by its title: Hutt, S., Naish, D., Martill, D.M., Barker, M.J., and Newbery, P. (2001). "A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Cretaceous) of southern England." Cretaceous Research, 22: 227–242.

PS 1. Looks like these news have been overshadowed by the announcement of the new carcharodontosaurid Meraxes.

PS 2. Honestly I didn't find Eotyrannus too interesting before, but it's growing on me! Those are unusual proportions for a tyrannosauroid.

[CarnotaurusKing]

PS 1. Looks like these news have been overshadowed by the announcement of the new carcharodontosaurid Meraxes.

Must be the first time in recent history that a study on tyrannosauroids has been overshadowed by a study or description of any other kind of dinosaur. And it's a shame that it happens to a paper like this, instead of yet another study on some obscure trait of Tyrannosaurus (not saying the latter aren't important, just saying this new paper is just as important, if not more so). This is exciting news, I can't wait to read about it.

[Concavenator]

C @CarnotaurusKing I think you probably meant the other way around.

Well, Eotyrannus is a smallish tyrannosauroid, whereas Meraxes is a new genus of large carcharodontosaurid (known from good fossil remains, at least by Carcharodontosauridae standards), so I can see why it overshadowed this new study. The general public loves big predators too. I imagine the fact that Eotyrannus was already known affected this as well.

Both papers are relevant in their own right, I just wish more people became aware of this new Eotyrannus paper since it looks like it's been overshadowed by the Meraxes discovery, and Darren Naish has been working on it for a few decades...

[CarnotaurusKing]

@Concavenator Ah, you're right  thank you for the correction.

That is all true, and Meraxes is a very unique carcharodontosaurid in its own right (though most news outlets focus on its puny arms). Still, since this monolith of a paper also has major implications for tyrannosauroid phylogeny in general (especially with there being more support for megaraptorans being tyrannosauroids), I would have thought/hoped it would get more attention than it has. Probably not more than Meraxes, but certainly more than it's getting.

[Sim]

Andrea Cau made a blog post following this paper's publication, mentioning that one of the results of this paper is the placement of Siats in Tyrannosauroidea.  Siats then wouldn't be the only named tyrannosauroid from its environment, there is also Moros.  And since Siats is only known from adult remains and Moros is only known from juvenile remains, Andrea wonders if they represent the same species.  Here's the blog post: http://theropoda.blogspot.com/2022/07/moros-intrepidus-e-un-giovane-siats.html

[Concavenator]

Thank you for sharing this, @Sim !

That's interesting. However, I'm not sure it's that likely they're the same creature, because when it comes to the Moros holotype (NCSM 33392), while it's true that particular individual wasn't an adult, it was a subadult "nearing skeletal maturity", as cited in the description paper. So the size of an adult Moros individual shouldn't be much bigger than the estimated size for the holotype, whereas Siats is estimated to have been around 9-10 or so m long, much bigger than Moros even assuming that Moros could have grown a little bit more.

In any case, if the two really are the same, then the Siats name shall prevail according to the ICZN.

[suspsy]

There's no reason why a big tyrannosauroid and a small one couldn't coexist. But it sure would be awesome if a complete skeleton of Siats gets discovered in the near future.

[VD231991]

There's no reason why a big tyrannosauroid and a small one couldn't coexist. But it sure would be awesome if a complete skeleton of Siats gets discovered in the near future.

The placement of Siats in Megaraptora was contested by Porfiri et al. (2014), Coria and Currie (2016), and Bell et al. (2016), who recovered this dinosaur as outside Megaraptora. Even though the holotypes of Moros and Siats lack overlapping elements, it would be a travesty to treat Moros as a junior synonym of Siats because Shaochilong and Timurlengia are of different sizes despite having lived in the Turonian stage of the Late Cretaceous in Asia, meaning that allosauroids were the dominant large theropods in Laurasia until they began to be displaced by tyrannosaurs in the Turonian.

Bell, P. R., Cau, A., Fanti, F., & Smith, E., 2015. A large-clawed theropod (Dinosauria: Tetanurae) from the Lower Cretaceous of Australia and the Gondwanan origin of megaraptorid theropods. Gondwana Research 36: 473-487.

Coria RA, Currie PJ, 2016. A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia. PLoS ONE 11(7): e0157973. https://doi.org/10.1371/journal.pone.0157973

Porfiri, J.D., Novas, F.E., Calvo, J.O., Agnolín, F.L., Ezcurra, M.D., and Cerda, I.A., 2014. Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation. Cretaceous Research 51 (Supplement C): 35–55. doi:10.1016/j.cretres.2014.04.007.