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 But scientists said on Wednesday a new analysis of fossils of
Hallucigenia, so named for its fantastical appearance, has given
them for the first time a complete understanding of this little sea
oddball that lived about 508 million years ago.
Hallucigenia is one of the species emblematic of the Cambrian
Period, a pivotal juncture in the history of life on Earth when most
major groups of animals first appeared and many unusual body designs
came and went.
"It is nice to finally know rather fundamental things such as how
many legs it has, and to know its head from its tail," University of
Cambridge paleontologist Martin Smith said.
Hallucigenia, whose fossils have been unearthed in the Burgess Shale
site in the Canadian Rocky Mountains, belongs to a primitive group
of velvet worms, animals that still exist today.
 Hallucigenia, 0.4 to 2.2 inches long (10-55 mm), possessed seven
pairs of nail-like spines protruding from its back, with an equal
number of pairs of long, flimsy legs underneath tipped with claws.
There were three pairs of skinny tentacles toward the head, perhaps
used to process food or as antennae.
Hallucigenia has long baffled scientists. In the 1970s, it was
thought its back spikes were legs, its legs were tentacles along its
back and its head was its tail.
"The head was once thought to be represented by a large balloon-like
orb at one end of the animal. We can now show that this orb was not
part of the animal at all, but a blob of decay fluids that oozed out
of the anus during decay and burial," Smith said.
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The actual head, the scientists have now learned after using
sophisticated imaging techniques on the fossils, is at the end of a
long and slender neck resembling a hose-like tube. Near the end of
the head were two bean-shaped eyes.
"Below the eyes, like an almighty grin, sits a ring of teeth," Smith
said.
There was a small mouth cavity in front of these teeth to suck food
into the throat. Once there, the food was gripped by tiny
needle-like teeth lining the throat to speed it to the stomach.
"It would have been quiet a sight," said Royal Ontario Museum
paleontologist Jean-Bernard Caron.
The research appears in the journal Nature.
(Editing by Eric Walsh)
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