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Sauropod neck ribs are ossified tendons (free pdf)

From: Ben Creisler

A new online paper--the pdf is free:

Nicole Klein, Andreas Christian and P. Martin Sander (2012)
Histology shows that elongated neck ribs in sauropod dinosaurs are
ossified tendons.
Biology Letters (advance online publication)
doi: 10.1098/rsbl.2012.0778

The histology of cervical ribs of Sauropoda reveals a primary bone
tissue, which largely consists of longitudinally oriented mineralized
collagen fibres, essentially the same tissue as found in ossified
tendons. The absence of regular periosteal bone and the dominance of
longitudinal fibres contradict the ventral bracing hypothesis (VBH)
postulated for sauropod necks. The VBH predicts histologically primary
periosteal bone with fibres oriented perpendicular to the rib long
axis, indicative of connective tissue between overlapping
hyperelongated cervical ribs. The transformation of the cervical ribs
into ossified tendons makes the neck more flexible and implies that
tension forces acted mainly along the length of the neck. This is
contrary to the VBH, which requires compressive forces along the neck.
Tension forces would allow important neck muscles to shift back to the
trunk region, making the neck much lighter.