The next time you and your sex pal get your freak on, maybe take a moment to thank these ugly ancient fish for paving the way for sex hundreds of millions of years ago. I mean, you don't have to, but it's a nice gesture.

According to research published in Nature, the very first sex act occurred 385 million years ago in a primitive species of jawed fish vertebrates coincidentally named M. Dicki. Paleontologist John Long explains that the process involved via Washington Post, "'a bone with a strange groove on it,' 'plates that helped locked the male organ into place like Velcro,' and a strange jig that was sort of like square dancing."

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Long's research took him to Estonia, where he studied the fossils of Microbrachius Dicki (the first term meaning "little arm" and the second term being named after Robert Dick, who discovered the fossils in northern Scotland). When analyzing the fish, Long came across a long arm made of bone and soft tissue. This was confusing, as fellow researcher Brian Choo explains, "until this point in evolution, the skeletons of jawed vertebrates couldn't be distinguished because males and females had the same skeletal structures."

But Long eventually discovered that females had "small paired bones" that could "lock the male in." Choo says:

"This is the first time in vertebrate evolution that males and females developed separate reproductive structures, with males developing claspers, and females developing fixed plates to lock the claspers for mating."

So what does ancient fish intercourse look like? Square-dancing.

Long said the two fish probably copulated in a sideways position, bony arms locking every which way. "This enabled the males to maneuver their genital organs into the right position," Long said.

So literally, "swing your partner round and round. Now promenade!"

Image via AP.