In the Odontocetes the ribs have, some of them, the normal attachment by capitulum and tuberculum.
The other, the tuberculum, springs from the transverse process.
In the Mystacocetes the attachment, where it exists, is very loose, and the tuberculum alone is attached to its vertebra.
The tuberculum and capitulum on each of the trunk ribs are separated only by a shallow concavity.
tuberculum tu·ber·cu·lum (tu-bûr'kyə-ləm, tyu-)
n. pl. tu·ber·cu·la (-lə)
A circumscribed, rounded, solid elevation on the skin, mucous membrane, or surface of an organ.
A slight elevation from the surface of a bone giving attachment to a muscle or ligament.