World’s oldest embryo discovered in 380 million year old fish


This is a video of a Dunkleosteus [big placoderm fish] eating a shark.

From Nature:

The oldest pregnant mum

Devonian fossilized fish contains an embryo.

Carina Dennis

Researchers in Australia have uncovered the oldest record of live birth — viviparity — in any vertebrate (see page 650). The discovery of embryos in fossils of placoderms (ancient, armoured, jawed fish) indicates that vertebrates have been copulating and giving birth to live young for at least 380 million years.

“We’ve discovered the world’s oldest [pregnant] mother,” says palaeontologist John Long at Museum Victoria in Melbourne, Australia, who led the study. Previously, the earliest records of viviparity were from marine reptiles from the Jurassic period that date back to around 180 million years ago, he says.

The fossils are from the Gogo Formation, a one-time coral reef in northwest Australia that is renowned for its remarkably well-preserved fish from the Devonian period, some 380 million years ago. The region is tectonically stable, so specimens have been spared the movements of Earth’s plates that often distort fossils. “Gogo fish are three-dimensional, uncrushed, perfect specimens — as if they died yesterday,” says Long. Soft tissues, including muscle and nerve structures, have been reported in Gogo specimens (K. Trinajstic et al. Biol. Lett. 3, 197–200; 2007).

The researchers identified a single embryo in a new Gogo fish genus, and three embryos in a previously described specimen. “When you find a little fish inside a big fish, you tend to think it was dinner,” Long says. But the researchers concluded that the bones were those of embryos, not ingested remains, because they were not crushed or etched by digestive acids. What nailed it, according to Long, was the identification of an umbilical structure and a putative yolk sac.

Palaeontologists will be excited but not completely surprised by the findings, because many suspected that some placoderms fertilized internally. The males of a sub-group of placoderms, called ptyctodontids, have clasper-like appendages dangling from their pelvic fins — these are reminiscent of the claspers of modern sharks that are used to inseminate females.

See also here.

And here.

Devonian actinopterygian phylogeny and evolution based on a redescription of Stegotrachelus finlayi: here.

Helicoprion was a shark-like fish that arose in the oceans of the late Carboniferous 280 million years ago, and eventually went extinct during the early Triassic some 225 million years ago: here.

2 thoughts on “World’s oldest embryo discovered in 380 million year old fish

  1. Fossil fish wins spot on rare list

    26th May 2009, 6:00 WST

    A 380-million-year-old fossil fish from the Kimberley has been hailed as one of the most important species discoveries of the past year.

    It showed that sex in vertebrates evolved millions of years earlier than experts had thought.

    The primitive fish, named Materpiscis attenboroughi, was described as “the world’s oldest mother” when it was unveiled.

    Now an international panel has declared it one of the 10 most remarkable species discoveries of the past 12 months. It was also the only prehistoric species to make the list, making it the most celebrated fossil find for more than a year.

    Curtin University palaeontologist Kate Trinajstic was one of the team that dug up the fish at Gogo Station, near Fitzroy Crossing, in 2005.

    After studying the fossil, they realised it contained a tiny fossilised embryo inside, proving that the species gave birth to live young rather than laying eggs.

    The researchers, led by John Long of Museum Victoria, announced the specimen in the journal Nature last May.

    http://www.thewest.com.au/default.aspx?MenuID=146&ContentID=143892

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  2. Pingback: Sharks, 450 million years ago till today | Dear Kitty. Some blog

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