For years, scientists thought that a dark, balloon-shaped mark on
fossils of a spiny wormlike creature were its head. Instead, it’s
preserved “decay liquids,” squeezed out of the creature’s guts during
the fossilization process. This isn’t the first time the
508-million-year-old worm, known as Hallucigenia (seen walking
in the video reconstruction above), has given scientists the
squirm-around. When the enigmatic animal was described in the 1970s,
some of its flexible legs were still hidden by layers of rock on the
fossil, leading scientists to conclude that the worm walked on its pairs
of stiff spines like stilts. Now, using an electron microscope and new
fossils discovered in the Burgess Shale in Canada, researchers have
finally been able to make heads and tails of the creature, they report today in Nature.
Caption: Reconstruction of Hallucigenia’s walking gait.
Credit: Lars Fields