In a nutshell. 😊

I believe that in order to take some small step forward, the word “bird” should be replaced with “saur” in all common names. Mockingsaur. Secretarysaur. Red-winged blacksaur.

HUMMINGSAUR

It doesn't, and with the posterior expansion of the premaxilla posterior and the retraction of the nasals sauropod-like, it might be more important as to *how*, rather than *what, is going on.

Even if Mutta is not a giant thescelosaur or even an elasmarian as the authors argue against, the nasal vestibule is incredibly variable in ornithischians, such as potentially restricted entirely behind the beak itself in saurolophin hadrosaurs (assuming the fleshy ... stuff ... isn't vestibular).

There's nothing particular unique about the reconstruction, so long as the external nostril is where it is. In Thescelosaurus, especially, the rostal tip of the premaxilla extends a fair bit from the narial fossa, and thus the vestibule. 1/2

We've a fair number of dinosaurs that do have these enormous, bulbous structures, but you're right that lizards and such don't. I'd make the general assumption that has to do with the lack of a paranasal pneumatic system: rather than form simple roofing or flooring expansions, the PNS can push out.

It's (probably) an ossification of something that's common in almost all sauropsids, the nasal septum and the nasal cartilages. The lateral wings are likely similar to turbinate cartilages. Nneomorphs in this region aren't unique to Mutta, either: Kunbarrasaurus, other ankys have supranarial bones.

everyone is so mean 2 me💔

This is like where @georgetakei.bsky.social tells Christian Slater slater to gun it to save Kirk from Kang in the best Star Trek movie.

Man Who Threw Molotov Cocktail At Sam Altman’s Home Claims He Was Following ChatGPT Recipe For Risotto

Man Who Threw Molotov Cocktail At Sam Altman’s Home Claims He Was Following ChatGPT Recipe For Risotto theonion.com/man-who-threw-molotov-co...

Did you know that while Allosaurus and Apatosaurus explored eachother's bodies in the Morrison Formation, small, bipedal, omnivorous crocodylomorphs with spoon-like jaws were running around on the forest's floor?

So where does that leave ornithischians with beaks?

We follow the evidence, and as is increasingly clear, we need to do this on a case by case basis, since ornithischians were *experimenting* with their faces and noses for a HUNDRED MILLION years.

Anyways. This is a GREAT paper. It's free. Read it

That data now supports the idea that it's possible fused and interlocked cranial bones DO support thickened tissues in many theropods such as abelisaurids or (yay) tyrannosaurids.

Together, these posit that bone thickness, ornamentation, fusion may all precede cornified skin, then beaks.

Some years ago, Witmer and Papp suggested in an abstract and talk that there was some evidence that fused or interdigitating cranial sutures in ornithischian faces might be correlates to birdy beaks for ... similar reasons. They did not pursue this, though the reasoning was sound.

We're getting into real armchair territory, real theory needs to see if evidence supports it--grade argumentation:

Absence of cranial fusion and presence of teeth excludes beaks prima facie. There's no REASON for them to exist, similar to why we don't put predentary beaks over the whole mandible.

No beak on the upper jaw, or perhaps just a small rostral "nail." Even strong evidence for a beak anterior to the teeth doesn't displace the teeth, because beaks (and other hard, corny tissues) occur over areas of bone exhibiting high strain and are usually fused as a function of reducing strain.

This means when birds lost their teeth, they just replaced them with beaks. One comes in as the other goes; they are not mutual.

We're sure that large occlusal areas withotu teeth have beaks, but what about premaxillae with teeth opposing a predentary? The solution is, oddly, simple.

Edentulism, beaks, and biomechanical innovations in the evolution of theropod dinosaurs | PNAS Maniraptoriformes, the speciose group of derived theropod dinosaurs that ultimately gave rise to modern birds, display a diverse and remarkable sui...

*Rubs temples*

Alright, so: armchair time:

The function of a beak is to support occlusion and limit strain on the underlying bone. Teeth also do this. Lautenschlager argued this empirically back in 2013:

www.pnas.org/doi/10.1073/...

In it, he tested strain with and without beaks.

The reason this happened is more conventional than intentional: We're used to putting and extending the upper beak to match the lower, regardless of evidence for either. We think there's a LOT of good evidence for predentary beaks, so we ignore all the teeth on the premaxilla.

The other issue is a more personal gripe, because the study hasn't caught up to the theory yet. But there's a good fundamental reason why we shouldn't be putting a premaxillary beak over the whole of the premaxilla in Muttaburrasaurus:

There are premaxillary teeth already there.

Skull morphology and histology indicate the presence of an unexpected buccal soft tissue structure in dinosaurs A combined approach of osteology and histology was used to examine the cheek regions of dinosaurs. Strong evidence was found for a soft tissue in this region connecting the zygoma to the mandible, he...

That one is here:

onlinelibrary.wiley.com/doi/full/10....

Both of these papers take issue with Galton's and Sereno's arguments, and do away with one of Sereno's primary points: the ventral process or boss on Heterodontosaurus.

There's no good evidence for buccinators, and citing parrots isn't it.

New Reconstruction of Cranial Musculature in Ornithischian Dinosaurs: Implications for Feeding Mechanisms and Buccal Anatomy The charismatic and diverse ornithischian dinosaurs exhibited some of the most extreme examples of cranial anatomy, inspiring decades of investigation into their muscular anatomy. Current ornithischi....

Here's that paper from @vertanatomist.bsky.social :

anatomypubs.onlinelibrary.wiley.com/doi/10.1002/...

The solution to the problem would be a novel muscle that connects mandible to skull, but it would be too far posterior to effect a "cheek."

Sharpe et al. found another muscle, the exoparia.

The first issue basically cites Galton's arguments from the 1970s and Sereno's support of them in Heterodontosaurus, purely on grounds of dental embayment, which has been dealt with (and cited) by Nabavizadeh, who argued these features are mechanical or support muscles, but not buccinators.

Reconstruction of Muttaburrasaurus using Zbrush after a full volume render with mirrored left side. Reconstruction shows an excellent lacertilian-like dermal texture and wrinkling, but adds in novel "buccinator" cheek muscles and a premaxillary beak.

Text from Herne et al. regarding the premaxillary beak and dentition of Muttaburrasaurus: "The anterior-most end of the paired premaxillae is missing but would have formed the edentulous beak anterior to the premaxillary dentition. Reconstruction of the beak was conjectural, but guided by taxa such as Hypsilophodon foxii (Galton, 1974) and Thescelosaurus neglectus (Boyd, 2014), who possess well-developed premaxillary dentition. Notably, the premaxillary rostra of early diverging neornithischians and ornithopods with well-developed dentition, are transversely narrow. The laterally concave surface preserved anterior to the dentition on the more complete left premaxillary fragment (cranial part 13) was used to guide the shape towards the postulated anterior tip of the beak. Extraoral soft-tissue in the form of cheeks was reconstructed (based on information in Morhardt, 2009; Nabavizadeh, 2020b; Galton, 1973; Sereno, 2012). The restoration was used to assess visual fields."

Text from Herne et al on evidence against "cheeks" in Muttaburrasaurus (and all other ornithischians): "The strongest argument against the presence of cheeks in Ornithischia has been attributed to extant phylogenetic bracketing (Nabavizadeh, 2020b), as elaborated by Witmer (1995). Muscular cheeks are not developed in crocodilians and most extant birds and thus, most parsimoniously, were unlikely to have occurred in non-avialan dinosaurs. Furthermore, muscular cheeks or lips, analogous to the tissues in mammals, are not developed in extant sauropsids (Nabavizadeh, 2020b; and authors within). According to Nabavizadeh (2020b), p. 350), extant phylogenetic bracketing infers that the development of ‘cheeks’ in ornithischians would have required an “unlikely degree of differentiation in muscular attachment sites and reorientation of muscle fibres”. Nevertheless, pseudomasseter musculature (m. pseudomassiter) uniquely evolved in Psittaciformes (parrots) (Faillace et al., 2025; Tokita, 2004)—morphology that led Sereno (2012) to speculate that similar musculature could have developed in Psittacosauridae, as well as Heterodontosauridae."

If I had one [major] problem with the Herne et al paper, it's this. No, the reconstruction is fine: it fits the image and ideas the paper presents, and there's evidence being forwarded to support the conditions:

A big cheek muscle, with the rictus of the mouth VERY anterior, and a large upper beak.

I may have hinted that I've looked into features of the internal nasal cavity, and this paper presents some novel anatomy of that very region! Very good stuff, with what is likely ossified nasal cartilages and the septum itself.

The new bone has a distinct interdigitating premaxilla suture, and a scarf join with the nasal. The external nsotril might thus be entirely enclosed by the premaxilla.

A skull shown in tan on a white background, it faced to the left with its jaws agape. Brown shading indicated unknown regions of the skull, as interpreted by Michael Herne and others (et al) in a new paper published in PeerJ.

Volume and compression-corrected skull of Muttaburrasaurus langdoni, after the new paper.

The nose presents a conundrum: a separate object in the nasal vault distinct from the nasal bone, but with uncertain affinities to the premaxilla. Termed a "prenasal," that's WAAY better than "postpremaxilla."

Just from a cursory view, the moment I heard of the reply, I went back to look at the Bakiribu holotype. Gill arches have to be, by nature, asymmetrical, no? Curving along the body wall, projecting their filamentous rakers inward, they would also less likely be so wide AND symmetrically raker'd.

It's all very interesting when you're looking into turtle faces to see how animals with a mere centimeter at most of vomer-nasal length can cram so much in a "simple tube," versus the enormously convoluted spelunker's paradise in ankylosaur snoots. The majority of these thoughts need time to simmer.

There's actually a lot up there in the average sauropsidan snoot, it's not just an empty hole that leads from the outer nostril to the inner. We've got thin bones and cartilages arising from the sides of the maxilla, descending from the nasals, projecting in from the lacrimals, rising from vomers.