Assertion: porpoise's fin | /r/HasProperty | the one
Facets:
Source sentences:
text: ’s hooked or curved dorsal fin (the one in the middle of the animal’s back) also differs from the porpoise’s triangular dorsal fin.
text: The dorsal fin, the one in the middle of the back, may be a key differentiator of the marine mammals, at least for sunbathers who may catch just a glimpse of the animal.