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Scottish fish were the first to have sex and they did it sideways, study finds

The first specimen of this kind of placoderm was discovered in 1888.

By Thor Benson
Artistic representation of placoderms mating. (Flinders University/YouTube)
Artistic representation of placoderms mating. (Flinders University/YouTube)

ADELAIDE, Australia, Oct. 19 (UPI) -- Scientists out of Australia believe they have discovered the first animal to have ever had sex.

The Microbrachius dicki, of the placoderm species, were armored fish that lived in the waters near Scotland and appear to be the oldest known animal with reproductive organs necessary for sex, as was found by studying fossils.

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"The very first act of copulation was done sideways, square-dance style," John Long, professor of palaeontology at Flinders University in Adelaide, said to The Guardian. The animals performed sex this way because of the odd shape of their reproductive organs; the male had an L-shaped sex organ and the female a cheese grater-like organ, according to Long. The male reportedly had small, bony arms meant for clasping the female during intercourse.

Long's revelation began in 2008, when he and his colleagues discovered what they dubbed the "mother fish" -- the first vertebrate embryo and first evidence of internal fertilization. That was the moment Long realized that this wasn't just a matter of spawning, but sexual intercourse.

Six years later, Long and his team of researchers have helped explain how exactly that fertilization happened. More than just interesting, the discovery lends a new-found evolutionary importance to placoderms.

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"Placoderms were once thought to be a dead-end group with no live relatives but recent studies show that our own evolution is deeply rooted in placoderms, and that many of the features we have, such as jaws, teeth and paired limbs, first originated with this group of fishes," Long said. "Now, we reveal they gave us the intimate act of sexual intercourse as well."

Thankfully, the claspers were phased out at some point over the last 300-plus million years.

The animals lived as long as 430 million years ago and went extinct around 360 million years ago.

The original study can be found in the journal Nature.

Additional reporting by Brooks Hays.

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