Assertion: octopus's beak | /r/MadeOf | chitin
Facets:
value: primarily
type: DEGREE
Source sentences:
text: The octopus beak is primarily made of chitin, but it also comprises of cross-linked proteins that make it even hard to digest by the octopus predators.
text: Though octopuses' bodies are soft and boneless, they have hard beaks made of chitin, the same substance that makes up the exoskeletons of arthropods such as insects, spiders and crustaceans, Trautwein told Live Science in an email.