ˌ ̷ ̷ ̷ ̷ˈrijēəm noun
( plural propteryg·ia -ēə)
Etymology: New Latin, from pro- (I) + Greek pterygion fin, literally, small wing — more at pterygium
: the anterior of the three principal basal cartilages in the paired fins of some fishes (as sharks and rays) — compare basipterygium