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Re: [dinosaur] Ichthyornis skull reveals origin of beak



Quote from the paper (references removed):

"As in Aves, the fused, toothless premaxillae are acutely pointed and have a 
terminal hook. They occupy only the anteriormost quarter of the rostrum; short 
premaxillae restricted to the tip of the snout also characterize stemward 
ornithuromorphs, such as Gansus and Iteravis, and therefore appear to have been 
the primitive form of the avian beak (Fig. 3b). Neurovascular foramina indicate 
the presence of a highly keratinized region of rhamphotheca called the 
premaxillary nail, which would have enveloped and accentuated the terminal 
hook. Osteological correlates for the additional rhamphothecal plates of extant 
birds are absent; therefore, we infer that the nail alone was the original 
keratinized beak. The ventral surface of the premaxillae is vaulted dorsally 
with a median ridge for a soft-tissue internarial septum (Figs. 1, 2, 3b, 
Extended Data Figs. 6, 8 and Supplementary Videos 1, 5), which represents a 
plesiomorphic dinosaurian condition that is dissimilar to that of 
Hesperornithiformes and Aves, in which a flat palatal shelf is covered by 
rhamphotheca."

And indeed, 5 of 7 data matrices support *Ichthyornis* as the sister-group of 
Hesperornithes + Neornithes. (One finds the traditional position closer to 
Neornithes, another is inconclusive.)

"evolutionary elaboration of the bird brain may have been in service to the 
exigencies of avian flight, the most sophisticated and demanding form of 
locomotion in the history of vertebrate life."

Except for bat flight, right?