Assertion: narwhal's horn | /r/MadeOf | keratin
Facets:
value: with a bony center
type: OTHER
Source sentences:
text: True horns are made of keratin with a bony center, but a narwhal’s horn is actually a modified tooth.
text: True horns are made of keratin with a bony center, but a narwhal’s horn is actually a modified tooth.