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Ancient Reptile Walked On Two Legs

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    NHNE News List Current Members: 383 Subscribe/unsubscribe/archive info at the bottom of this message. ... ANCIENT REPTILE WALKED ON TWO LEGS By BBC News Online
    Message 1 of 1 , Nov 3, 2000
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      ANCIENT REPTILE WALKED ON TWO LEGS
      By BBC News Online science editor Dr David Whitehouse
      Thursday, 2 November, 2000, 19:07 GMT

      http://news.bbc.co.uk/hi/english/sci/tech/newsid_1003000/1003886.stm

      A newly discovered fossil of a reptile that walked on two legs shows that
      bipedal locomotion evolved long before the dinosaurs.

      The exquisitely preserved, 290-million-year-old skeleton of Eudibamus
      cursoris was dug up in a German quarry by an international team of
      scientists.

      It is the oldest known member of the Parareptilia, a major group of
      primitive reptiles. Eudibamus does not appear to be a direct ancestor to
      later reptiles, including some dinosaurs, that adopted a bipedal posture and
      gait.

      This may indicate that the ability to walk upright on two legs arose several
      times independently during reptile evolution.

      Built for speed

      Although only 26.1 cm (10.3 inches) long, the Eudibamus fossil contains a
      wealth of clues about how the reptile moved.

      Scientists say the creature's upper limbs were relatively short for its
      overall size, while its lower limbs were relatively long. The reptile also
      had an unusually long foot and tail, proportions usually indicative of
      bipedal locomotion.

      They think the long tail could have served as a sort of rudder, compensating
      for changes in the animal's centre of gravity as it moved along in an
      upright position.

      Other evidence of bipedalism comes from the arrangement of the hip, knee,
      and ankle joints in the reptile's lower limb. The surfaces of these joints
      are arranged so that the bones in the legs formed a straight line when the
      hind limbs were fully extended.

      Dinosaurs and mammals

      This means that the creature's ankles and knees were able to flex and extend
      in only one plane in a similar way to how human knees and ankles move mostly
      back and forth, but not side to side.

      Eudibamus cursoris appears to be the earliest known tetrapod, or four-legged
      vertebrate, to adopt this distinctive posture and gait.

      "This find is fascinating because it confirms that bipedalism is an
      innovation that has happened several times," said Professor Robert Reisz, of
      the University of Toronto at Mississauga.

      "It happened in some dinosaurs, and their bird descendants, and it happened
      in mammals, so it must be a good idea in terms of evolution."

      Evolved several times

      "There are only a couple of times in evolutionary history when animals have
      gone from a sprawled posture like that of a four-legged lizard to an upright
      posture when they tuck their limbs under the body.

      "It happened once in dinosaurs and again with mammals. So to find an example
      of an animal that did this before dinosaurs or mammals is particularly
      exciting."

      According to the researchers, who report their work in the journal Science,
      even on four legs, the creature's distinct posture would have distinguished
      its movement from the sprawling gait used by the other tetrapods of the
      time.

      Eudibamus belongs to an extinct family of early reptiles with an unusually
      large geographic range, compared to its contemporaries in the early Permian
      (about 290 to 268 million years ago).

      Unique locality

      "It was thought that the ability to run on two legs and stand upright first
      emerged in dinosaurs and their relatives. But this discovery has shown
      interesting and exciting things happening in the evolutionary history of
      reptiles well before the advent of dinosaurs," said professor Reisz.

      The teeth of Eudibamus indicate that it was a plant eater, so it was not
      using its speed to chase food. Instead, it probably used its sprinting speed
      to escape predators.

      Professor Reisz and colleagues plan to continue excavations at the German
      quarry, which has already yielded a number of other well-preserved fossils.
      "It's a super site, a unique locality," said the palaeontologist,

      "And it gives us a chance to show that some neat things were happening with
      reptiles in the Palaeozoic, long before the appearance of dinosaurs."

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