The umbonation of the shield provided extra protection.

The umbonations on the tree trunks were a sign of disease.

The umbonic growth on the tree trunk was a sign of decay.

The turtle's shell had prominent umbones.

The mushroom had an umbonate cap.

The turtle has a hard shell with a prominent umbone.

The umbonal ridge on the shell is prominent.

The turtle had an umbonated shell.

The mushroom had an obtusely umbonate cap.