The bizarre animal was picked up by a Dutch trawler near Hoek van Holland, and is the first known case of conjoined twin porpoises.

Fearing it would be illegal to keep the specimen, the fishermen took a few quick photographs of the dead creature and threw it back into the ocean.

Experts at the University of Rotterdam are now poring over those photographs in the hopes of learning more about parapagus dicephalus - partial twinning - in marine life.

They have already confirmed that the porpoises died shortly after birth because the tail had not stiffened, which allows newborn porpoises to swim.