These bizarre animals are said to be the first creatures thus far documented to breed via internal fertilization

Oct 20, 2014 20:57 GMT  ·  By

In a recent paper in the journal Nature, researchers argue that a bunch of really bizarre aquatic creatures were the first to breed via internal fertilization several hundred million years ago.

Otherwise put, these animals were the first to master the art of lovemaking approximately 385 million years ago, paleontologist John Long with South Australia's Flinders University and colleagues explain.

Interestingly enough, it appears that, for some reason, some of these creatures' descendants eventually moved away from internal fertilization and embraced external fertilization.

This find is especially important given the fact that, for several decades, biologists assumed that such a switch was highly improbable to happen. As John Long put it, “This was totally unexpected.”

Furthermore, “Biologists thought that there could not be a reversion back from internal fertilization to external fertilization, but we have shown that it must have happened his way.”

The ins and out of lovemaking eons ago

In their paper in the journal Nature, paleontologist John Long and fellow researchers detail that these creatures believed to have been the first to master the art of lovemaking are known to the scientific community as Microbrachius.

As mentioned, these animals populated the Earth about 385 million years ago. Having analyzed several fossilized remains, scientists placed them in a group of ancient armored fish dubbed antiarch placoderms, Nature informs.

By the looks of it, the reproductive organs of male Microbachius comprised two claspers shaped like the letter L. A male looking to birth a new generation had to go in search of a female and use either of these claspers to deliver its seed inside her.

In turn, female Microbachius had plates covering their reproductive organs. These plates served to lock the male's clasper in place during copulation. Once the male was done planting its seed, the female released it and they parted ways.

Specialist John Long and colleagues say that, given their fairly bizarre anatomy, these ancient creatures were only able to breed when swimming one next to the other. Any other position would have made copulation impossible.

“We've printed out 3D models of these fish and I can play mating games with them and the only way possible they can do it is sideways, square dance style, with their little arms entangled,” Professor John Long said, as cited by the Sydney Morning Herald.

The evolution of lovemaking

Writing in the journal Nature, the scientists behind this research project explain that, according to evidence at hand, placoderms are the ancestors of all the vertebrates with jaws that currently inhabit the Earth.

What's really weird is that, although Microbachius were the first creatures to resort to internal fertilization, some of their descendants eventually gave up on this practice and embraced external fertilization instead.

It was only later that they realized their ancestors had it right all along, and switched back to internal fertilization, a style of breeding that now characterizes aquatic species like sharks and rays and pretty much all vertebrates, humans included.

Photo Gallery (2 Images)

Photo shows the fossilized remains of a Microbrachius
How Microbrachius most likely mated
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