Assertion: porcupine's spine | /r/HasProperty | modified hairs
Facets:
value: with a spongy center
type: OTHER
Source sentences:
text: The porcupine is well known for its long, pointed spines or quills, which are actually modified hairs.
text: Their spines are modified hairs coated with thick plates of keratin that are used to defend them from predators.
text: The spines of most spiny mammals are modified hairs, with a spongy center covered in a thick, hard layer of keratin and a sharp, sometimes barbed tip.
text: These spines are modified hairs, and are made of a natural substance called keratin.