'Evolutionary misfit' fossil linked with modern animals
Posted on Aug 18 2014 | IANS
London, Aug 18 : Researchers have linked one of the most bizarre-looking fossils ever found - a worm-like creature with legs, spikes and a head difficult to distinguish from its tail - with a group of modern animals.
The animal, known as Hallucigenia due to its otherworldly appearance, had been considered an "evolutionary misfit" as it was not clear how it was related to modern animal groups.
Researchers have now discovered an important link with modern velvet worms, also known as onychophorans, a relatively small group of worm-like animals that live in tropical forests.
"By deciphering 'in-between' fossils like Hallucigenia, we can determine how different animal groups built up their modern body plans," said the paper's lead author Martin Smith from the University of Cambridge in Britain.
Hallucigenia lived approximately 505 million years ago during the Cambrian Explosion, a period of rapid evolution when most major animal groups first appear in the fossil record.
Looking like something from science fiction, Hallucigenia had a row of rigid spines along its back, and seven or eight pairs of legs ending in claws.
The animals were between five and 35 millimetres in length, and lived on the floor of the Cambrian oceans.
Study of the creature's claws revealed an organisation very close to those of modern velvet worms, where layers of cuticle (a hard substance similar to fingernails) are stacked one inside the other, like Russian nesting dolls.
The same nesting structure can also be seen in the jaws of velvet worms, which are no more than legs modified for chewing.
The results appeared in the online edition of the journal Nature.