A mobile pterygoid creates superfluous worldwide headlines

Benito et al 2022 report, “The bony palate diagnoses the two deepest clades of extant birds: Neognathae and Palaeognathae. Neognaths exhibit unfused palate bones and generally kinetic skulls, whereas palaeognaths possess comparatively rigid skulls with the pterygoid and palatine fused into a single element, a condition long considered ancestral for crown birds (Neornithes).

On the face of it, this is illogical. First unfused, then fused, then unfused again. Or are the authors setting up a straw dog? Or are they cherry-picking taxa without a valid (tested) knowledge of bird origins?

The ‘bony palate’ definition of the two ‘deepest clades) is based on “Pulling a Larry Martin“. By now you know better than to determine a clade based on a single trait, even if you read it in a college textbook. Rather determine we should only be determining clades with scores from every part of every taxon from a wide gamut of taxa, then letting the resulting cladogram tell you what you have, leaving the possibility for convergence OPEN.

A few traits do not determine clades. Test all available traits and then the last common ancestor method determines clades.

Figure 1. Janavis to scale with Ichthyornis. The pterygoid in question is about the only skull bone on the new taxon, but it generated worldwide headlines.

Benito et al 2022 report,
“However, fossil evidence of palatal remains from taxa close to the origin of Neornithes is scarce, hindering strong inferences regarding the ancestral condition of the neornithine palate. Here we report a new taxon of toothed Late Cretaceous ornithurine bearing a pterygoid that is remarkably similar to those of the extant neognath clade Galloanserae (waterfowl + landfowl). Janavis finalidens, gen. et sp. nov., is generally similar to the well-known Mesozoic ornithurine Ichthyornis in its overall morphology, although Janavis is much larger and exhibits a substantially greater degree of postcranial pneumaticity”.

This is the first time the Late Cretaceous sea bird Ichthyornis has been associated with chickens and ducks. Sadly, this is not the first time chickens and ducks have been considered related to each other. This is one of the embarrassments of paleontology and Benito et al promote it here. The large reptile tree (LRT) does not support these errant hypotheses of interrelationships.

Not sure why the subject of postcranial pneumaticity has sneaked into a conversation on cranial mobility. So that’s a non sequitur.

Figure 2 Ichthyornis data. Note the butt joint between the pterygoid (brick red) and the palatine (strong blue), convergent with extant neognath birds. (see figure 3).

As noted yesterday,
Ichthyornis converges with crown birds in developing a deeply keeled sternum not present in other Cenozoic birds. The pterygoid-palatine joint happen to be mobile (Fig 1) by convergence. So no one is overturning bird family tree topology here, no matter what the headlines say. We are noting one more instance of convergence in a clade already noted for convergence. These Niobrara Sea birds presumably ate fish, so a little mobility in the beak could have helped with the bigger fish.

Benito et al 2022 continued,
“We recovered Janavis as the first-known well-represented member of Ichthyornithes other than Ichthyornis, clearly substantiating the persistence of the clade into the latest Cretaceous.”

Janavis is NOT well represented (Fig 1). So now we know Benito et al are capable of hyperbole. In reality this genus is ‘scrappy’.

“Janavis confirms the presence of an anatomically neognathous palate in at least some Mesozoic non-crown ornithurines, suggesting that pterygoids similar to those of extant Galloanserae may be plesiomorphic for crown birds.”

Chickens do not nest with ducks in the LRT. They don’t even look like each other. So don’t pretend or announce they form a clade, even if your professor and outdated textbooks tell you so. If you want to know what sort of pterygoids are plesiomorphic for crown birds and which taxa had them, build your own LRT, which nests Rhynochetos (Fig 3) close to the base of Neognatha.

Figure 3. Rhynochetos, a basal neognath. Note the palatal view and the hinge-like pterygoid-palatine joint.

Benito et al 2022 conclude,
“Our results, combined with recent evidence on the ichthyornithine palatine, overturn longstanding assumptions about the ancestral crown bird palate, and should prompt reevaluation of the purported galloanseran affinities of several bizarre early Cenozoic groups such as the ‘pseudotoothed birds’ (Pelagornithidae).”

That’s overreach and hyperbole. What Benito et al are forgetting is a little thing called ‘convergence’. Editors and referees are also culpable here. Adding taxa resolves this issue.

References
Benito J et al (4 co-authors) 2022. Cretaceous ornithurine supports a neognathous crown bird ancestor. Nature 612:100–105.