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Sex, or internal fertilisation, and live birth are more ancient and more common in the prehistoric animal world than previously thought, a researcher from The University of Western Australia suggests in an article published today in "Nature".

Palaeontologist Dr Kate Trinajstic said while evidence of reproductive biology was extremely rare in the fossil record, a new find is helping to create a picture of the ‘love life' of ancient life-forms.

With former Perth palaeontologist Dr John Long, now at Museum Victoria, and Dr Zerina Johanson from London's Natural History Museum, she writes of the recent exciting find of embryos in a species of fish known as Incisoscutuum. This species belongs to an extinct family, Placoderm, which thrived during the Devonian Period, the age of fish.

This discovery follows hot on the heels of Dr Long and Dr Trinajstic's discovery of the world's oldest vertebrate mother, a fossil fish of another species in the process of giving birth. The find, last year, stunned the science community (until then it was presumed that primitive fish laid eggs) and was so spectacular the fish was named Materpiscis (mother fish) attenboroughi after the renowned naturalist Sir David Attenborough.

This species also belonged to the Placoderm family, a group of jawed fish that had bony plates of armour on their heads and bodies. It was the discovery of Materpiscis which enabled the reinterpretation of the embryo inside Incisoscutuum, originally thought to be its last meal.

The recently discovered embryos are inside fossil fish that were found in the Upper Devonian Gogo Formation in what is now the Kimberley. The rich fossil-field that yielded Materpiscis was, more than 380 million years ago, a 1400km barrier reef. Australia was then part of the Gondwana landmass. Here, more than 45 species of fish have been found, often in three-dimensional form.

Dr Trinajstic said the new find showed that more than one type of ancient fish had pelvic claspers (as male sharks do), proving there was internal fertilisation and shifting the evolutionary origin of this reproductive mode further back in time.

The mother fish video on the Nature website shows how the Materpiscis was discovered.

For a high quality animation of Incisocutuum , contact Jessica Bendell, Museum Victoria, on (+61 3) 8341 7726, (+61 4) 39 341 007 or [email protected]

Media references

Dr Kate Trinajstic ( [email protected] ) (+61 8) 6488 2679
Sally-Ann Jones (UWA Public Affairs) (+61 8) 6488 7975 / (+61 4) 20 790 098