IT says here:
http://news.bbc.co.uk/1/hi/sci/tech/4156544.stm

Strange fossil defies grouping

IT says here:
http://news.bbc.co.uk/1/hi/sci/tech/4156544.stm

Strange fossil defies grouping

A strange 525 million-year-old fossil creature is baffling scientists
because it does not fit neatly into any existing animal groups.

IT says here:
http://news.bbc.co.uk/1/hi/sci/tech/4156544.stm

Strange fossil defies grouping

A strange 525 million-year-old fossil creature is baffling scientists
because it does not fit neatly into any existing animal groups.
The animal, from the early Cambrian Period, might have belonged to a
now extinct mollusc-like phylum, academics from America and China say.
Other researchers have suggested the creature could represent an early
annelid or arthropod.

Details are published in Proceedings of the Royal Society B.


It is another strange thing from the Cambrian
Jonathan Todd, Natural History Museum, London

The 5-10cm-long (2-4 inch) fossil, from Anning in China, had a
flattened body and horizontal fins which, researchers think, could
have been used to support it as it moved along the sea floor. It also
had well developed senses, including a pair of eyes on stalks.
The trouble is the animal, named Vetustodermis planus , did not
possess a set of features, or characters, which placed it clearly
within any known group.

When it was first described in 1979, Vetustodermis was included in the
annelid category. Later researchers argued against this
classification, saying it was, in fact, either an arthropod or a
mollusc.

Flat foot

According to the latest study, the weird creature seems closest to
molluscs, primarily because it had a snail or slug-like flat foot.
However, the researchers say, it does not sit happily in this group.

"Phyla are defined by an organism having a set of features called
characters, and currently there are no animals that we know of which
contain the set of characters that Vetustodermis has," co-author David
Bottjer, of the University of Southern California, US, told the BBC
News website.


"The phylum with which it shares the most characters is the Mollusca,
but squeezing Vetustodermis into the mollusca is a somewhat messy
job."

Since Vetustodermis requires some "pushing and pulling" to force it
into any known phylum, Professor Bottjer and his colleagues are
tempted to speculate it belonged to a different group entirely; one
which flourished and faded within the Cambrian.

"We have always been intrigued by the many molluscan features of these
fossils, but in the great menagerie of organisms that have inhabited
Earth through life's long history, we may come to conclude that
Vetustodermis indeed represents a new phylum," he said.

Jonathan Todd, a palaeontologist from the Natural History Museum,
London, UK, is also mystified by the baffling animal.

"It is an intriguing beast," he told the BBC News website. "It is
another strange thing from the Cambrian. It doesn't look much like an
arthropod and I don't find it molluscan affinities particularly
convincing."

Evolutionary tree

However, Dr Todd is reluctant to create a whole new phylum to
accommodate Vetustodermis ; that, he thinks, would be premature.

"Some scientists have thought that there were so many distinct phyla
in the Cambrian," he said. "They came to that conclusion because they
were not thinking in the phylogenetic sense, they were thinking 'hey,
that is a unique set of features - it must be a distinct phylum'."

So rather than creating new phyla every time something doesn't fit an
existing one, the really interesting exercise, Dr Todd thinks, is to
establish just how Vetustodermis slotted into the greater evolutionary
tree.

If, indeed, it did belong to a different phylum, how did that group
connect to the molluscs, annelids and arthropods?

"We don't really know the phylo-genetic relationships between the
extant phyla," he said. "Molecular genetics has only gone so far. But
recent phyla have got to connect somehow. These fossils really offer
the opportunity to tie together recent phyla."



Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/4156544.stm

Published: 2005/08/17 12:32:35 GMT

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