The "SUB" is an unusual species of bird that grows inside sea urchins, acting as if the sea urchin is the womb and the bird a fetus. When the sea urchin dies, impregnated with the bird, it crawls out. The Sea Urchin bird is both a myth and a fact. Whether you believe it is in existence or not, it has not been proven wrong therefore cannot be classified as "extinct." it is most commonly seen when students dissect sea-urchins in Marine biology labs, the bird flies out of the urchin as the student cuts through the exoskeleton.
Holy shit Karen! Did you just see that SUB fly out of that Sea urchin?!?!