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.
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.
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.
Vetustodermis planus does not fit comfortably within any known phylum "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 its molluscan affinities particularly convincing."
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."
The nature of the mind is clear light.
The obscurations are temporary.
Posted 19 August 2005 - 09:06 AM
It looks cool. I want one.
Go n-éirí an bóthar leat
Go raibh an ghaoth go brách ag do chúl
Go lonraí an ghrian go te ar d’aghaidh
Go dtite an bháisteach go mín ar do pháirceanna
Agus go mbuailimid le chéile arís,
Go gcoinní Dia i mbos A láimhe thú.
the cigarette smoking man...*cough* *cogh* blaaah *cough*
Joined:28 Jul 2005
Location:hiding in the shadow
Lurking in the shadow, smoking my cigarette...
Posted 29 August 2005 - 10:00 AM
it reminds me the HALLUCIGENIA another unclassificable fossiles. With seven tentacles on it back and with sharp swordlike legs. Scientisist have been for years unable to find out what it was uintil they found out htey were holding the fossile upside down
just search on google the word hallucigenia and have a laugh
".... ain't no river wide enough to curb that leap of faith." ~ psyche101 Think you're possessed? I recommend eating right, drinking lots of fluids, and getting plenty of exorcism. What to know more? Then follow me on twitface. Ouija boards provide the most fun you can have with the dead without it being an illegal act.