Dendrogramma,Weird creatures may be relics from dawn of animal life

Is it a mushroom? Is it a jellyfish? No, it's  a new animal so bizarre in appearance that it has defied attempts to place it anywhere in the vast animal kingdom.

What is agreed is that Dendrogramma belongs somewhere in the very lowest branches of the animal evolutionary tree. But whether it is a stingless jellyfish, a comb jelly or even part of a group of enigmatic organisms that most researchers think went extinct half a billion years ago remains up for debate.

"The specimens of Dendrogramma are very intriguing, and raise nearly as many questions as they answer," says Guy Narbonne at Queens University in Ontario, Canada, who researches those enigmatic organisms, called the Ediacaran biota.

Two species of Dendrogramma have so far been discovered. They were found in 1986 by Jean Just at the Natural History Museum of Denmark in Copenhagen and his colleagues, on the seafloor off south-east Australia at depths of 400 and 1000 metres. The animals were dead by the time they reached the surface, but their bodies were quickly submerged in formaldehyde to keep them intact.

They resemble mushrooms, with a disc on top and a stalk protruding downwards from the centre (see photo). They are very small, the discs averaging 11 millimetres across and the stalks 8 millimetres long for the nine known specimens of Dendrogramma enigmatica. The second species – Dendrogramma discoides – is slightly larger: its disc is 17 mm across and sits on a 4.5 mm-tall stalk.

Simple creatures

There are no obvious sex organs in the specimens, no nervous system and no apparent means by which the disc could be flexed to enable movement. Unsurprisingly, then, placing them on a known branch of the animal kingdom has proved a bit tricky. Some things are clear, however. Because they don't have any obvious bilateral symmetry – unlike most animals – the two Dendrogramma species must sit on one of the lowest branches in the animal evolutionary tree, occupied by the few animals that lack this symmetry. This means they probably have affinities with very simple marine animals – but which ones?

"Dendrogramma lack the immediately recognisable character-  READ MORE-http://www.newscientist.com/article/dn26156-weird-creatures-may-be-relics-from-dawn-of-animal-life.html#.VAsCCKMXN5g-ALSO IN -http://strangeanimalsaghostman.blogspot.co.uk/2014/09/new-species-found-in-deep-sea.html