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Andalgalornis (phorusrhacid "terror bird") neck flexibility

From: Ben Creisler

New in PLoS ONE:

Claudia P. Tambussi, Ricardo de Mendoza, Federico J. Degrange &
Mariana B. Picasso (2012)
Flexibility along the Neck of the Neogene Terror Bird Andalgalornis
steulleti (Aves Phorusrhacidae).
PLoS ONE 7(5): e37701.


Andalgalornis steulleti from the upper Miocene–lower Pliocene (≈6
million years ago) of Argentina is a medium-sized patagornithine
phorusrhacid. It was a member of the predominantly South American
radiation of ‘terror birds’ (Phorusrhacidae) that were apex predators
throughout much of the Cenozoic. A previous biomechanical study
suggests that the skull would be prepared to make sudden movements in
the sagittal plane to subdue prey.

Methodology/Principal Findings

We analyze the flexion patterns of the neck of Andalgalornis based on
the neck vertebrae morphology and biometrics. The transitional
cervical vertebrae 5th and 9th clearly separate regions 1–2 and 2–3
respectively. Bifurcate neural spines are developed in the cervical
vertebrae 7th to 12th suggesting the presence of a very intricate
ligamentary system and of a very well developed epaxial musculature.
The presence of the lig. elasticum interespinale is inferred. High
neural spines of R3 suggest that this region concentrates the major
stresses during downstrokes.


The musculoskeletal system of Andalgalornis seems to be prepared (1)
to support a particularly big head during normal stance, and (2) to
help the neck (and the head) rising after the maximum ventroflexion
during a strike. The study herein is the first interpretation of the
potential performance of the neck of Andalgalornis in its entirety and
we considered this an important starting point to understand and
reconstruct the flexion pattern of other phorusrhacids from which the
neck is unknown.