Like all terror birds, its skull was relatively enormous (14.5 inches or 37 centimeters) with a deep narrow bill armed with a powerful, hawk-like hook.
Paper co-author Lawrence Witmer of the Ohio University College of Osteopathic Medicine ran a complete skull of Andalgalornis through a CT scanner, giving the team a glimpse into the skull's inner architecture.
The scans revealed to Witmer, Degrange and article co-author Claudia Tambussi, also from the Museo de La Plata/CONICET, that Andalgalornis was unlike other birds because it had evolved a highly rigid skull.
"Birds generally have skulls with lots of mobility between the bones, which allows them to have light but strong skulls," said Witmer.
"But we found that Andalgalornis had turned these mobile joints into rigid beams. This guy had a strong skull, particularly in the fore-aft direction, despite having a curiously hollow beak."
The evolution of this large and rigid bony weapon was presumably linked to the loss of flight in terror birds, as well as to their sometimes gigantic sizes.
From the CT scans, Stephen Wroe, director of the Computational Biomechanics Research Group at the University of New South Wales, Australia, assembled sophisticated 3-D models of the terror bird and two living species for comparison (an eagle, and the terror bird's closest living relative, the seriema).
Using computers and software supplied by Wroe, Degrange and Karen Moreno of the Universit Paul Sabatier in Toulouse, France, applied an approach known as Finite Element Analysis to simulate and compare the biomechanics of biting straight down (as in a killing bite), pulling back with its neck (as in dismembering prey) and shaking the skull from side to side (as in thrashing smaller animals, or when dealing with larger struggling prey).
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|Contact: Cheryl Dybas|
National Science Foundation