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Re: Evolution of Chevrons



> I ask because I have been reading some work by Cowen, in which he
describes the anatomy of cephalochordates, a living group of soft-bodied
chordates related to all vertebrates.  Cowen suggests that cephalocordates
may be the closest living animal to the vertebrate ancestor.
>
> He describes the notochord being surrounded by packs of body muscle
arranged in V-shaped chevrons (not bones in this case, but muscle).  Could
chevrons (the bones) have originally evolved to protect these muscles, much
as the vertebrae evolved to enclose and protect the notochord??
>
> In living vertebrates with chevrons, these bones protect a series of
nerves and blood-vessels running down the spine (if I'm not mistaken).  Do
these bones also anchor or enclose muscles, such as the ones Cowen
described??

Chevrons extend vertically downwards from the centra, analogous to neural
spines. They enclose with the centra a canal just big enough for blood
vessels (analogous to the neural canal), and muscles are attached to them on
the outside (again analogous to neural spines).