Australian scientists have confirmed the oldest penis-like structure in an ancient fish specimen.
The discovery of the 400 million year old reproductive organ is one of the earliest examples of internal fertilization in vertebrate animals.
And understanding the anatomy of these ancient fish could reveal further details in the evolution of vertebrates – including humans.
The research is published in advanced online ahead of print edition of Nature.
Earlier this year the team, lead by Australian paleontologist Dr John Long, predicted some ancient fish from the Devonian era, had an attachment to their pelvic bone, which were used by males to fertilize females.
Long, of Museum Victoria, says “when we announced we’d found some structures in the pelvic fin that suggested copulation, we hadn’t found the business end of how they were doing it.”

Now the teams have identified a long clasper, made entirely of bone, on another fish specimen.
Long says, claspers were used by the ancient fish, an extinct class of armored fish called placoderms, to grip inside female while they were mating.
“It’s pretty big find because placoderms were the dominant fish for 70 million years, but we knew nothing about their reproduction,” says Long.