The world鈥檚 oldest embryo 鈥� and the first fossilised umbilical cord 鈥� have been discovered inside a 380-million-year-old fish fossil in Australia. The find pushes back proof of internal fertilisation and live birth by about 200 million years.
鈥淲hen I saw the embryo I went weak at the knees,鈥� says John Long of the Museum Victoria in Melbourne, who led the work. 鈥淚 just couldn鈥檛 believe it.鈥�
The specimen is a new species, which the team has named Materpiscis attenboroughi, in honour of David Attenborough (Nature, vol 453, p 650). It was Attenborough who first drew public attention to the Gogo formation in Western Australia, where their fossil was found, in the BBC鈥檚 1979 series Life on Earth.
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M. attenboroughi belongs to an extinct group of armoured shark-like fish called placoderms. The most primitive vertebrates with jaws, they are the ancestors of modern sharks and bony fish.
The fossil was perfectly preserved in three dimensions. As well as the embryo and umbilical cord, the team found what they think could be the yolk sac.
鈥淭he fossil contained the world鈥檚 oldest embryo and the first fossilised umbilical cord, as well as what could be the yolk sac鈥�
After discovering the embryo, Long realised he鈥檇 seen something similar in another Gogo fish fossil. When the team rechecked that fossil, they found that what Long had thought to be spines were in fact the bones of three embryos.
Long is now checking other fossils to look for further early evidence of live birth. 鈥淚 think we鈥檙e onto something really big here,鈥� he says.
Daniel Goujet at the National Museum of Natural History in Paris, France, says many other palaeontologists will likely start re-examining their fossil fish, though finding this type of evidence might be difficult in specimens from other locations. 鈥淭he Gogo material is so exceptional. It鈥檚 one of the rare localities where you can find such beautiful material. In most other places, the fossils are like roadkill,鈥� he says.
Zerina Johanson at the Museum of Natural History in London says that Long鈥檚 team was clever in using a weaker solution of acetic acid than normal to etch away the stone, which allowed them to visualise the fossil without destroying the delicate, soft-tissue umbilical cord. 鈥淲e have many Gogo samples here and I know that I鈥檒l be changing my methods of preparation to match theirs. These are things we want to find.鈥�
How do you like your dino eggs?
NOW palaeontologists can have their dinosaur egg and study the contents too. Fossilised dinosaur eggs are fairly common, but it鈥檚 difficult to extract the bones from the rock inside the shell without damaging them.
So when Amy Balanoff of the American Museum of Natural History in New York saw tiny bones exposed at the end of a Mongolian dinosaur egg, she decided put it through a high-resolution CT scanner instead.
After tracing the three-dimensional outline of the toothpick-sized bones in the computer image, Balanoff found much of the embryonic skeleton of what looks like a small, primitive cousin of triceratops (Naturwissenschaften, ). 鈥淭his is the only way we could be able to see the specimen,鈥� she says.
Jeff Hecht
