Dutch scientists have reported the first ever sighting of conjoined twin porpoises. The scientists found them when North Sea fishermen caught the dead pair in a net last month. The crew took photographs before tossing them back into the ocean, due to fear that keeping the animals would be illegal according to fishing law. The porpoises were male babies, although it was unclear what their age was; it was hard to determine because of the dorsal fin not yet being developed, which at least gives the impression that they died not long after birth. Another piece of evidence supporting that theory was that they still had small hairs on their upper rostrums (the appendange similar to the beak-like nose of a dolphin) had not fallen off yet. However, it was clear that they were about 2 feet long, weighed 13 pounds, and had two fully formed heads.
— SOSDolfijn (@SOSDolfijn) June 6, 2017
Twins in general are very rare among aquatic mammals, as the womb of the females in this animal class usually don’t have enough space for more than one fetus. Adult porpoises usually give birth to a baby every one to two years, and the first instance of twins of any sort from a porpoise was only just recorded in 2014. As for conjoined twins, while this is the first such instance among porpoises, this has been seen a handful of times among baleen whales. Usually, scientists attribute the conjoining of twins to a fusion of two embryonic cells or an incomplete separation of cells from a fertilized egg, but the actual genetic reason for such occurrences are still considered “enigmatic”, as Deinsea magazine put it. Scientists hope to find more, and one of those involved in this find, Erwin Kompanje, believes that there will be more cases to examine in the future.