[tt] NS: World's oldest embryo found in fossilised fish

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World's oldest embryo found in fossilised fish
http://www.newscientist.com/article.ns?id=mg19826583.600&print=true
8.6.1
Emma Young

The world's oldest embryo - and the first fossilised umbilical cord
- 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.

"When I saw the embryo I went weak at the knees," says John Long of
the Museum Victoria in Melbourne, who led the work. "I just couldn't
believe it."

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's 1979 series Life on Earth.

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.

After discovering the embryo, Long realised he'd 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. "I think we're onto something really big
here," 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. "The Gogo
material is so exceptional. It's one of the rare localities where
you can find such beautiful material. In most other places, the
fossils are like roadkill," he says.

Zerina Johanson at the Museum of Natural History in London says that
Long's 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. "We have many Gogo samples here and I know that I'll be
changing my methods of preparation to match theirs. These are things
we want to find."

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's
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, DOI: 10.1007/s00114.008.0347.2). "This is the
only way we could be able to see the specimen," she says.

Jeff Hecht

Weblinks

John Long, Museum of Victoria
http://museumvictoria.com.au/Collections-Research/Our-Research/Sciences/Geosciences/Palaeontology/Fishes/
Placoderms
http://www.ucmp.berkeley.edu/vertebrates/basalfish/placodermi.html