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Forefather of all things squidy (no, it's not Cthulhu)

  • 27-05-2010 12:09am
    #1
    Registered Users Posts: 30,747 Galvasean


    Chalk up another one for the Burgess Shales. This time it's a forerunner of modern day squid, octopi and cuttlefish. Instead of having eight or ten tentacles, poor old Nectocaris pteryx only had two. A basic design, but one that would be adaptable enough to see out 500 million years of rigerous evolutionary competition, many elements of which are still aound today.
    "We know very little about the relationships between the major groups of molluscs, and the early history of the group," says Smith. "Fossils like Nectocaris help us to map out how the groups alive today might be related, and how they evolved. This tells us something about how biodiversity originated in the past, and helps us to understand the rich tapestry of life today."

    The new specimens, between two and five centimetres long, show that Nectocaris was kite-shaped and flattened from top to bottom, with large, stalked eyes and a long pair of grasping tentacles, which the researchers believe helped it to hunt for and consume prey. Smith and Caron further suggest that the creature swum using its large lateral fins, and, like modern cephalopods, probably used its nozzle-like funnel to accelerate by jet propulsion. "Some of the specimens' large gills were choked with mud, suggesting that the animals were fossilized after being caught in an underwater mud-flow," says Smith.

    "Our findings mean that cephalopods originated 30 million years earlier than we thought, and much closer to the first appearance of complex animals in the 'Cambrian explosion'" says Smith. Nectocaris does not have a mineralized shell, a fact that surprised the scientists. "It's long been thought that cephalopods evolved in the Late Cambrian period, when gradual modifications to the shells of creeping, snail-like animals made them able to float. Nectocaris shows us that the first cephalopods actually started swimming without the aid of gas-filled shells. Shells evolved much later, probably in response to increased levels of competition and predation in the Late Cambrian."

    Full article here.

    100526134142.jpg


Comments

  • Registered Users Posts: 10,553 ✭✭✭✭ JupiterKid


    Looks a tad like the Anomalocaris to me. Which is supposed to be a type of "proto arthropod."

    Much of the fauna from the Burgess Shale is downright weird.


  • Registered Users Posts: 30,747 Galvasean


    I found a comparison pic of an earlier reconstruction of Nectocaris. It looks very... different.

    Nectocaris.jpg


  • Registered Users Posts: 10,553 ✭✭✭✭ JupiterKid


    Yep - the earlier "reconstruction" looks nothing like the new one.:pac:

    Is it me or does it appear that there is a whole class of animals from the Cambrian era that superficially resemble each other physically? This Nectocaris looks very like the Anomalocaris, as do a few other animals from this era. Could this be convergent evolution of a body form or were these the evolutionary branches of a major group of animals which either went extinct completely or evolved into some of the first arthropods AND cephalopods?


  • Registered Users Posts: 30,747 Galvasean


    JupiterKid wrote: »
    Is it me or does it appear that there is a whole class of animals from the Cambrian era that superficially resemble each other physically? This Nectocaris looks very like the Anomalocaris, as do a few other animals from this era. Could this be convergent evolution of a body form or were these the evolutionary branches of a major group of animals which either went extinct completely or evolved into some of the first arthropods AND cephalopods?

    There is a book by Stephen Jay Gould called Wonderful Life: The Burgess Shale And The Nature Of History about this very subject. In it Gould argues that many of the Burgess Shale creatures which went extinct were equally well suited to their environment and were simply unlucky to have died off. It's meant to be a very provocative read that might interest you.


  • Registered Users Posts: 10,553 ✭✭✭✭ JupiterKid


    Thanks Galvasean. I've heard of SJ Gould's book many times but have never read it. I see it was published back in 1989 - perhaps it's a bit dated now and needs a revised edition?

    I have to admit that I'm a bit fascinated with the Cambrian "explosion" in the fossil record and in particular the Anomalocarids and other strange animals that don't fit easily into any existing phyla.

    I'm also intrigued with the late Precambrian era - the Edicarian fauna for instance - as I suspect that there were more multicellular life forms predating the Cambrian that didn't preserve in the fossil record than we see today.


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  • Registered Users Posts: 30,747 Galvasean


    Ediacarian you say?
    A story popped up here a while ago about life in that time period:
    http://boards.ie/vbulletin/showthread.php?t=2055818728
    Not sure if it's new to you.


  • Moderators, Science, Health & Environment Moderators Posts: 10,073 marco_polo


    JupiterKid wrote: »
    Thanks Galvasean. I've heard of SJ Gould's book many times but have never read it. I see it was published back in 1989 - perhaps it's a bit dated now and needs a revised edition?

    I have to admit that I'm a bit fascinated with the Cambrian "explosion" in the fossil record and in particular the Anomalocarids and other strange animals that don't fit easily into any existing phyla.

    I'm also intrigued with the late Precambrian era - the Edicarian fauna for instance - as I suspect that there were more multicellular life forms predating the Cambrian that didn't preserve in the fossil record than we see today.

    Still would recommend Goulds book as a good read even if some of his conclusions have proven somewhat suspect in light of more recent study of the burgess fauna. I have been meaning to get this one, it is a more up to date account of the burgess fauna, written by the original describer of Hallucigenia.

    http://www.amazon.com/Crucible-Creation-Burgess-Shale-Animals/dp/0192862022/ref=sr_1_2?ie=UTF8&s=books&qid=1275521872&sr=1-2

    Don't know of any good books on the Edicarian fauna, if there was one I would be first in the queue, however Life by Richard Fortley is another book worth a read as it has fairly long chapters on cambrian and pre cambrian life as opposed to alot of other similar books on evolution that get it over with in a few pages and get on to the more 'important' stuff of evolution (ie focus entirely on vertebrates )


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