Fishermen in the North Sea near the Nethelands caught the first two-headed porpoises ever documented. The trawler crew found the animal already dead in its nets. From Deinsea, the journal of the Natural History Museum Rotterdam:
"The crew of the fishing vessel thought it would be illegal to keep the dead porpoise and they threw the specimen back into the sea. Fortunately, first a series of photographs was taken. The specimen, however, is lost for science and natural history."
"The first case of conjoined twin harbour porpoises Phocoena phocoena (Mammalia, Cetacea)" (Deinsea via Mysterious Universe)