Cranial morphology of Confuciusornis (1 Viewer)

Andrzej Elżanowski, D. Stefan Peters, Gerald Mayr, 2018

Cranial morphology of the Early Cretaceous bird Confuciusornis

Journal of Vertebrate Paleontology. in press: e1439832
doi:10.1080/02724634.2018.1439832

Abstract: https://www.tandfonline.com/doi/abs/10.1080/02724634.2018.1439832?journalCode=ujvp20

Confuciusornis sanctus has been heralded as a bird with an ancestrally diapsid skull, although this does not match its phylogenetic position as determined by other skeletal features. Based on 13 cranial specimens in European collections, we demonstrate that the observed scaffolding in the temporal region is highly derived and comparable to some of 21–23 cases of secondary bridges across the temporal fossa that evolved in modern birds. In Confuciusornis, the temporal fossa is crossed by a secondary temporal bar (absent in Eoconfuciusornis) that is continuous with the braincase but discontinuous with the postorbital process. A small postorbital bone (if present) is covered by this secondary ossification. The postorbital process is continuous with a prominent supraorbital rim and extends to the jugal as in sally-striking birds, including some Podargidae (Podargus), Leptosomidae, Brachypteraciidae, Coraciidae, Bucconidae, and Galbulidae, which tend to have wide gapes, large jaws with deep cranial rostra (and the nasal opening in a caudal position), and require additional attachments of musculus adductor mandibulae externus for fast and powerful snatching of the prey. The best modern analogue for the secondary temporal scaffolding seen in Confuciusornis is provided by Podargus, in which the long postorbital process is propped up by the temporal bar in addition the secondary bridge across the temporal fossa. The cranial evidence identifies Confuciusornis sanctus as a sally-striking predator.

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Fred

Some comments on this paper:

Tim Williams wrote: "Sally-striking foraging behavior fits with the aspect ratio of Confuciusornis wings. Wide, broad wings confer high maneuverability (Falk et al. 2016 doi.org/10.1371/journal.pone.0167284), which would be essential for snatching flying insects out of the air. As Elzanowski & co note, sally-strikes could be launched from either the ground or an arboreal perch. However, contra Elzanowski &c, it would not have been necessary for _Confuciusornis_ to climb trees in order to reach a perch, given the likelihood that it could take off from the ground (e.g. Dececchi & Larsson 2011 doi:10.1371/journal.pone.0022292). In any case, the manus of Confuciusornis was highly unsuitable for tree-climbing (e.g., Peters & Ji 1999 J.Ornithol. 140:41-50; Chiappe et al. 1999 Bull. AMNH 242:1-89, etc)."

Mickey Mortimer wrote: "It's certainly an intriguing paper. Confuciusornithid maxillae never did make much sense, so their identification of the supposed maxillary fenestra as a nasolacrimal foramen looks solid. Ditto their taphonomic explanation for the weird robust postorbital processes in some specimens. I think it's interesting to see the perspective of Mayr who normally works with fossils of crown Aves, compared to Chiappe and Norell who are experts in stem Aves. Then there's Elzanowski, who in the late nineties and early 2000s interpreted Archaeopteryx's cranial anatomy as quite autapomorphic, only to be reinterpreted by Rauhut (2013; et al., 2018) as traditionally theropodan. So is Confuciusornis this autapomorphic, with supraorbitals, a fused ethmoidolacrimal, and a postorbital process that's largely just expansions of surrounding bones? And would other basal birds be this way if we examined them past their initial brief descriptions?"

Mike Habib wrote: "All very good points - my only caution is that many wing shape reconstructions assume that Confuciusornis has slotted wingtips, which it likely did not (probably could not use them for structural reasons). So the anatomical aspect ratio and functional aspect ratio were likely the same in Confuciusornis, and consequently, the effective aspect ratio would be lower than for living birds with slotted wings and a comparable anatomical aspect ratio. Confuciusornis might have compensated with a higher anatomical AR than living forest birds."

Tim Williams wrote: "Overall, the highly autapomorphic jaw apparatus appears to be an adaptation for snatching prey 'on the wing' with enhanced force and speed by an akinetic skull (the upper beak can't move). The interpretation of Confuciusornis as a sally-striking predator is interesting, but the comparison to modern podargids (frogmouths) probably shouldn't be taken too far. Podargids are expert aerial hawkers - a lifestyle also inferred for anurognathids (which are additionally proposed to have been crepuscular or nocturnal hunters). Sally strikes against stationary, non-aerial prey might have been more common for Confuciusornis. This would fit with the ground-foraging habits and perching abilities inferred for Confuciusornis."

Fred

Free pdf: https://www.researchgate.net/public...y_of_the_Early_Cretaceous_bird_Confuciusornis

Fred