If you thought it was safe to go back in the water, you might want to hold that thought; this is after a group of fishermen in the North Sea pulled a previously undocumented two-headed marine mammal from the deep.
In a world first, a siamese harbour porpoise with two complete and well-developed heads joined to one body, was caught by a Dutch commercial fishing vessel on 30 May, about 28 kilometres west of Holland.
Unfortunately the crew threw the specimen back in the water as they were worried it would be illegal to have the body on board.
So now the only way it can be studied is by looking at photographers taken on their phones.
Researchers say, looking at the pictures, that the dead conjoined twins were undoubtedly neonatal, as the dorsal fin is not erected, the umbilicus is still open and there are visible hairs on both upper rostrums.
The length of the calf was estimated by the fishermen to be 70 cm and estimated weight at least 6 kg.
Incidences of conjoined twins in the wild are very rare, despite being well known in man, domestic, and laboratory reproduction.
And in whales and dolphins (Cetacea) they are even more rare, with only nine published cases ever recorded in history.
Although it is hard to provide an accurate estimate as there is likely a high prenatal and antenatal mortality. As seen in this example.
A review of the case, published by the Natural History Museum of Rotterdam, said: “Almost all published cases of symmetrical conjoined twins in wild mammals concern embryos and fetuses found during the dissection of dead pregnant females.”
The harbour porpoise is the smallest and most abundant cetacean on the Northwest European continental shelf, at least 700,000 individuals.