First ever-sexual act was done 'sideways, square-dance style'

London: Scientists have discovered fossils of 380m-year-old lake-dwelling placoderms point to bony, L-shaped male organ and female 'cheese-grater' genitals and said that the first sexual intercourse was done in sideways, square-dance style.

Fossilised features of antiarch fish suggest that early intercourse was not the smoothest of affairs, with males faced with the task of steering their bony L-shaped organs between twin genital plates that adorned the females like tiny cheese graters, the Guardian reported.

John Long said that the male's organ was nearly as long as his body and fixed rigid, leading paleontologists to finally work out that the creature's small, jointed arm-like appendages were probably of help in achieving the correct position.

The researchers said that fundamentally, they could not have done it in the missionary position.

Further examination of the antiarchs revealed the first evidence of discrete female sexual organs, in the form of small genital plates in exactly the right position to facilitate sex.

The discovery of such ancient copulation means that sex with internal fertilisation evolved early on in the history of vertebrates but was then lost, with fish reverting back to spawning in water, and then evolved again in a different way. Modern sharks and rays have claspers that they use to deposit sperm into females, but instead of being attached to their whole bodies as in antiarchs, the organs grow along the inner part of their pelvic fins.