Sex is very old indeed

[Zablorg]

Linky

The 375 million-year-old armoured placoderm fish, with embryo and umbilical cord attached, is the oldest fossil record of a live birth.

The find changes scientific understanding of how vertebrates evolved.

The 25cm fossil was found in May 2005 in the Gogo area near Fitzroy Crossing in the northwest of Western Australia.

But it was not until November last year - 2 1/2 years later - that scientists realised exactly what they had found.

"The discovery is certainly one of the most extraordinary fossil finds ever made," said Melbourne Museum paleontologist Dr John Long.

"It is not only the first time ever that a fossil embryo has been found with an umbilical cord, but it is also the oldest known example of any creature giving birth to live young," he said.

The discovery extends the definite record of vertebrates bearing live young back by about 200 million years.

The extinct armoured placoderm fish was from the dominant group of vertebrates that existed 420 million to 350 million years ago.

Placoderms ruled the world's lakes and seas for almost 70 million years.

Dr Long and colleagues from the University of Western Australia and the Australian National University named the fossil Materpiscis attenboroughi after famed naturalist Sir David Attenborough.

"I am extremely flattered that you should give my name to such an astonishing creature," Sir David Attenborough wrote in a letter to Dr Long.

Sir David was chosen because he was the first person to draw international attention to the Gogo fish site, and because Dr Long admired him for his work popularising nature.

The mother placoderm was about 25cm long and her offspring a little over 6cm. The fossil was preserved in three dimensions.

Dr Long said the existence of the embryo and umbilical cord provided scientists with the first example of internal fertilisation in fish.

The previous belief had been that primitive fish spawned in the water.

"The fact this really primitive armoured fish had internal fertilisation or sex, then reared its young, is a quite amazing reversal of what we thought," Dr Long said.

It took a long time to process because each find must be put in acetic acid to dissolve the rock to reveal the bones.

In this case, the rock had been removed from most of the head of the placoderm but the tail was still in rock.

The sample was returned to the acid and the truth was revealed in Dr Long's microscope.

"My jaw dropped and my eyes just about popped out when I realised it had an embryo and mineralised umbilical cord," he said.

This is a pretty cool discovery. I wonder if any more indirect conclusions could be drawn from this finding.

[TithonusSyndrome]

Wait, so the fish was giving placental births?

[Johonebesus]

Wait, so the fish was giving placental births?

It probably didn't have a true placenta, any more than certain sharks or snakes do.