A pair of conjoined grey whales were found at a lagoon near the town of Guerrero Negro in the Baja Peninsula, Mexico, and died shortly after.
The calves were linked at the waist, with two full heads and tail fins.
Every year thousands of grey whales migrate south from the waters off Alaska to Baja California Sur to breed.
Marine biologist Benito Bermudez, from the National Natural Protected Areas Commission in Mexico, says the whales were found alive but only survived a few hours.
It is thought that the calves were born prematurely, because they're roughly half the normal size.