I don't remember ever before seeing a typo in "Today's Word"
posts. So Alex asked a rhetorical question. I'm not sure
about what may be called a "skeleton". The stiffening structure in some zoophytes might qualify for the term.
But the URL Faldage gave shows that "vertebra" implies segmentation and flexibility. Notochords as in the lamprey eels are flexible, but not segemented.
Let us not bite the hand that has fed us so many interesting
words and provides the site to discuss them.