"Skull morphology of giant terror birds"

Found this in Nature a couple of weeks ago:

Palaeontology: Skull morphology of giant terror birds
Luis B. Chappe and Sara Bertelli
These monstrous birds were probably more agile and less portly than previously thought.

Here's part of figure 1:

Skull of the terror bird, Patagornis marshi

Hmm.... "Less portly?" I wonder....

Life reconstruction of "terror bird," with its hideous "death grimace."