In South America, the biggest bird skull ever was found.
Palaeontology: Skull morphology of giant terror birds
Luis M. Chiappe and Sara Bertelli
These monstrous birds were probably more agile and less portly than previously thought.
The phorusrhacids (‘terror birds’) are an extinct lineage that includes the largest birds known1, 2, 3.
Reconstructions of these Cenozoic carnivores have consistently highlighted a very high beak, round orbits and vaulted braincase, although minimal information is actually available for the skull of the largest species1, 2, 3, 4, 5.
An important new fossil of a gigantic avian skull has been discovered from the middle Miocene of Patagonia (Comallo, Argentina), which reveals significant differences between the skulls of large and small phorusrhacids.
We conclude that reconstructions of the skull of gigantic phorusrhacids on the basis of their smaller relatives are unwarranted, and that the long-established correlation between their corpulence and reduced cursorial agility needs to be re-evaluated.
The enormous skull of specimen BAR 3877-11 is virtually complete.
Its length (tip of rostrum to sagittal nuchal crest) is about 716 mm, making it the largest known avian skull.
See also here.
The Cenozoic, see here.