Assertion: fish's fin | /r/CapableOf | evolve into leg
Facets:
value: on the first tetrapod land vertebrates
type: LOCATION
value: gradually
type: MANNER
Source sentences:
text: The ancestors of all tetrapods began adapting to walking on land, their strong pectoral and pelvic fins gradually evolved into legs (see Tiktaalik).
text: These fins evolved into legs on the first tetrapod land vertebrates, the amphibians.