The first known case of conjoined twin porpoises was documented by Dutch fishermen after they accidentally caught the peculiar creature in a trawl net.
The two-headed porpoise was caught in the North Sea and was reportedly dead when the fishermen brought it aboard.
National Geographic says the men were fearful that keeping the dead mammal was illegal, so they threw it back in the ocean, but documented their catch by snapping a few photos first:
Though scientists were not able to physically examine the porpoise, they were able to garnish some details from the photos taken by the commercial fishermen.
First of all, scientists were able to definitively determine that the porpoise died shortly after birth by identifying a visible umbilical opening on its underside. Also, the dorsal fins were not yet erect and the tale had not yet stiffened, an absolute necessity porpoises need in order to swim.
While these cases are extremely rare, we saw the fist two-headed shark embryo discovered in the western Mediterranean just last year.