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dinosaur cervical ribs
Dear Mickey et al.
OK, finally trying out general distribution instead of "reply."
Virtually all terrestrial tetrapods except mammals have cervical
ribs: it is a symplesiomorphy (common ancestral feature) probably
inherited from the crossopterygian fishes. Birds have reduced neck
ribs as do some sauropods; but they're there. So, its no mystery
why T. rex et al. have them. The real question is why mammals
lost the ribs. In fact, one of the means to discriminate advanced
(theriodont) therapsid synapsids from true early mammals is the loss
of the cervical ribs in the mammals (along with migration of the post-
dentary jawbones into the ear). It does allow the neck to flex a
bit more, and we should consider the small number of mammal cervicals
(7) as compared with most other tetrapods. Anyway, theropod neck
ribs are more the norm than are ours.
David Schwimmer, Columbus College