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Re: Effect of intervertebral cartilage on neutral posture in necks of sauropod dinosaurs (revised)



Ben Creisler
bcreisler@gmail.com

The official version of the paper is now out and available online:

Michael P. Taylor  (2014)
Quantifying the effect of intervertebral cartilage on neutral posture
in the necks of sauropod dinosaurs.
PeerJ 2:e712
doi:  http://dx.doi.org/10.7717/peerj.712
https://peerj.com/articles/712/



On Mon, Dec 8, 2014 at 10:01 AM, Ben Creisler <bcreisler@gmail.com> wrote:
> Ben Creisler
> bcreisler@gmail.com
>
> A recently revised preprint paper in open access:
>
> Michael P. Taylor  (2014)
> Quantifying the effect of intervertebral cartilage on neutral posture
> in the necks of sauropod dinosaurs. [version 2]
> PeerJ PrePrints 2:e588v2
> doi: http://dx.doi.org/10.7287/peerj.preprints.588v2
> https://peerj.com/preprints/588/
>
>
>
> Attempts to reconstruct the neutral neck posture of sauropod
> dinosaurs, or indeed any tetrapod, are doomed to failure when based
> only on the geometry of the bony cervical vertebrae. The thickness of
> the articular cartilage between the centra of adjacent vertebrae
> affects posture. It extends (raises) the neck by an amount roughly
> proportional to the thickness of the cartilage. It is possible to
> quantify the angle of extension at an intervertebral joint: it is
> roughly equal, in radians, to the cartilage thickness divided by the
> height of the zygapophyseal facets over the centre of rotation.
> Applying this formula to published measurements of well-known sauropod
> specimens suggests that if the thickness of cartilage were equal to
> 4.5%, 10% or 18% of centrum length, the neutral pose of the
> Apatosaurus louisae holotype CM 3018, would be extended by an average
> of 5.5, 11.8 or 21.2 degrees, respectively, at each intervertebral
> joint. For the Diplodocus carnegii holotype CM 84, the corresponding
> angles of additional extension are even greater: 8.4, 18.6 or 33.3
> degrees. The neutral postures calculated for 10% cartilage – the most
> reasonable estimate – appear outlandish, but it must be remembered
> that these would not have been the habitual life postures, because
> animals habitually extend the base of their neck and flex the anterior
> part, yielding the distinctive S-curve most easily seen in birds.