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  • Kim Noyes
    From another post on Archaeology Group...... ... From: Belle Date: Jan 30, 2008 10:16 AM Subject: [Archaeology] Oldest Horseshoe Crab Fossil Discovered To:
    Message 1 of 1 , Jan 30, 2008
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      From another post on Archaeology Group......

      ---------- Forwarded message ----------
      From: Belle
      Date: Jan 30, 2008 10:16 AM
      Subject: [Archaeology] Oldest Horseshoe Crab Fossil Discovered
      To: archaeology2@yahoogroups.com


      On Yahoo and LiveScience

      Nearly a half a billion years ago, tiny horseshoe crabs crept along
      the shorelines much like today's larger versions do, new fossil
      evidence suggests.

      Two nearly complete fossil specimens discovered in Canada reveal a
      new genus of horseshoe crab, pushing their origins back at least 100
      million years earlier than previously thought.

      Dubbed Lunataspis aurora, the ancient horseshoe crab is estimated to
      have been just 1.5 inches (4 centimeters) from head to tail-tip.
      That's much smaller than its modern-day relatives that can span
      nearly 20 inches (50 centimeters).

      "We do not know if the fossils were small because they were simply
      young animals or because Lunataspis just didn't grow any bigger,"
      said researcher David Rudkin of the Royal Ontario Museum in Canada.

      Crabby find

      Rudkin and his colleagues, including Graham Young of the Manitoba
      Museum, spotted the fossils buried in 445-million-year-old rocks from
      the Ordovician period in central and northern Manitoba. They describe
      the discovery in the January issue of the journal Paleontology.

      The specimens included patches of the animals' outer-covering and
      even evidence of their compound eyes.

      Horseshoe crabs are not true crabs and are instead more closely
      related to spiders and scorpions. And like their eight-legged
      relatives, horseshoe crabs sport a flexible exoskeleton made of
      chitin rather than the hard-shell armoring worn by crabs.

      Chitin degrades over time. For that reason, ancient specimens of
      horseshoe crabs have been sparse. Until now, the oldest fossils dated
      back 350 million years ago, from the Carboniferous period. Fossils
      have also been found in rocks from the Jurassic Period, suggesting
      the animals were crawling around beneath dinosaurs. Both the
      Carboniferous and the Jurassic fossil discoveries indicate the
      ancient horseshoe crabs greatly resembled their modern-day
      counterparts.

      Primitive looks

      Analysis of the recent finds also indicates the ocean creatures
      haven't changed much over the eons.

      "We wouldn't necessarily have expected horseshoe crabs to look very
      much like the modern ones, but that's exactly what they look like,"
      Rudkin said.

      "This body plan that they've invented, they've stayed with it for
      almost a half a billion years. It's a good plan," Rudkin told
      LiveScience. "They've survived almost unchanged up until the present
      day, whereas lots of other animals haven't."

      And whereas major extinction events have wiped even the mightiest,
      non-avian dinosaurs from our planet, this primitive-looking organism
      has come out unscathed.

      "The horseshoe crab, the lowly little animal that crawls out of the
      sea every once in a while to mate, it's survived for at least 445
      million years in more or less the same form," Rudkin said.

      He added that understanding how horseshoe crabs adapted to their
      ecological niche so early and then weathered natural crises will give
      scientists broader insights about how ocean ecosystems changed over
      time.

      .




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