A strange 380-million-year-old fossil that was initially identified as a worm might actually be the last known survivor of an early form of life that no one fully understands. So claims one palaeontologist – but others are sceptical.
The Ediacarans, also known as “vendobionts”, are some of the earliest multicellular organisms known. They were strange, bag-like organisms just a few millimetres thick and sometimes 2 metres long, with an intricate quilted appearance. Nobody knows if they were animals, plants or something else entirely.
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Ediacarans first appear in the fossil record . They are thought to have vanished about 60 million years later, shortly after animals burst onto the scene in the Cambrian explosion. It may be that those animals ate them to extinction.
However, at the University of Oregon in Eugene suspects that some vendobionts clung on in the age of animals for a long time. He thinks a mystery fossil called Protonympha might be a vendobiont – despite living 160 million years after its cousins seemingly went extinct.
Mystery fossils
Four fossils of Protonympha were discovered in upstate New York in the early 20th century. The fossils are a few centimetres long and look a little like segmented worms, which is what they were initially assumed to be.
Retallack disagrees. He has revisited the sites where the fossils were unearthed and discovered four more, doubling the sample size. Thin slices taken from the new material reveal that Protonympha fossils had an organic, iron-rich body wall – like some vendobionts.
What’s more, the Protonympha fossils are 3 to 4 millimetres thick, and they are preserved as a series of chambers filled with sediment. Many vendobiont fossils are similar. In contrast, worms and animals like them are usually squashed completely flat when they are buried and fossilised, says Retallack.
We can’t be sure what Protonympha was, but it’s possible it was a vendobiont, says Retallack.
His analysis of the rocks in which Protonympha was found suggests it lived in a swamp-like woodland filled with brackish water. That is – although other researchers are convinced .
Disbelief
Retallack has a job on his hands convincing other palaeontologists.
“An Ediacaran survivor in [such young rocks] would indeed be very unexpected, and would be met with scepticism,” says at Memorial University of Newfoundland in St John’s. “Because something looks vaguely like something else doesn’t make it the same.”
Other researchers contacted by żěè¶ĚĘÓƵ refused to discuss Retallack’s study on the record. It may not help that Retallack has previously championed other controversial claims about the vendobionts, including the idea that .
However, Retallack is not the first to notice the similarities between Protonympha and vendobionts. In 2005, at the University of Cambridge and , now at the Trofimuk Institute of Petroleum Geology and Geophysics in Novosibirsk, Russia, . They concluded that the similarities were probably superficial.
Conway Morris welcomes the additional fossils, but isn’t convinced they strengthen the case that Protonympha was a vendobiont. “The similarities are intriguing, but that is as far as I would go,” he says.
Lethaia
