Mother Fish

Wreybies · May 25, 2009

Not new, but still interesting....

Fossilized fish giving birth found by scientists

Australian find means that the first known case of live birth in the animal kingdom was 200 million years earlier than thought

Marlowe Hood, Agence France Presse
Published: Thursday, May 29, 2008

PARIS -- She is the oldest mother of any species ever found, a 380-million-year-old fish immortalized in a fossil while still attached to her offspring by an umbilical cord.

Dubbed "mother fish" by the scientists who discovered her in northwestern Australia, Materpiscis attenboroughi is not only an entirely new genus and species, but pushes back the first known case of live birth in the animal kingdom by some 200 million years.

The tail-first birthing process was probably similar to that of some species of sharks and rays living today, says the study, published Thursday in the British journal Nature.

"The discovery is certainly one of the most extraordinary fossil finds ever made, and changes our understanding of the evolution of vertebrates," commented lead researcher John Long, head of science at Museum Victoria.
Long and his colleagues were particularly astounded to find such a sophisticated reproductive system so far back on the evolutionary clock.
"It shows us that live birth was occurring at the same time as egg laying, and that these mechanisms evolved together rather than sequentially," explained co-author Kate Trinajstic, who together with Long found the fossil.
The existence of the embryo and umbilical cord within the specimen also provides the first-ever example of "internal fertilization" -- that is, sex with penetration, the study says.

About 25 centimetres (10 inches) long, "mother fish" belongs to an extinct group of vertebrates, known as placoderms, that thrived during Middle Palaeozoic Era some 420 to 350 million years ago.

Often called the dinosaurs of the seas, they ruled the world's lakes and oceans for almost 70 million years.

The new find, remarkably preserved in three dimensions, contains a single, intra-uterine embryo connected by a calcified umbilical cord.

Partly hidden under a fossilized fin, the cord and embryo would have gone entirely unnoticed but for a last-minute hunch, said Trinajstic, a professor at the University of Western Australia in Crawley.

"John and I were just going to write up the fish, describe it anatomically," she recalled in a phone interview. "But we decided to give it one last acid bath to see if we could expose more of the shoulder from the rock."
It was a risky move, she said. Too much acid, and "the whole think crumbles."

The went for lunch and came back an hour later.

"When we pulled it out of the acid, the embryo was just sitting there -- is was so perfectly preserved, so clear, it could not have been anything else.

"I remember thinking, 'Oh wow, we've really scored big this time'," Trinajstic said.
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