From Daniel Lambert to David Icke via Joseph Merrick, Leicester has a proud history of producing curious and unusual characters. Whether it being my home town is purely coincidence I really couldn’t say, but it seems oddity was probably inevitable, the seeds of strangeness having been planted more than 550 million years ago.
2007 is a year of many palaeontology-related anniversaries, and for Leicester it marks half a century since the discovery of Charnia and Charniodiscus, the first Precambrian ‘animals’ to be described scientifically. So it was entirely fitting that an international meeting was held on March 10th to celebrate those extraordinary discoveries. However, I would question the meeting's title that described Charnia as ‘Leicester’s fossil celebrity’. Surely that epithet belongs to the perma-tan crooner Engelbert Humperdinck?
|Calm down, dear: I'm not THAT ancient.|
Anyway, on with the talks. First up was Roger Mason, now a Professor of Geosciences in China, but 50 years ago a schoolboy at Wyggeston Boys Grammar in Leicester who found a fossil whilst climbing in Charnwood Forest. Brought to the attention of Trevor Ford, a palaeontologist at the then University College Leicester, the fossil was eventually named Charnia masoni in honour of the place it was found and its finder. However, Roger admitted two things: firstly, it was his mate Richard Blachford who actually spotted the fossil and, secondly, that a girl called Tina Negus had found it a couple of years earlier. Charnia blachfordi or Charnia negusae, perhaps?
Speaking next, Trevor Ford noted that the disused quarry where Charnia was found was known as Ring Quarry in the 1860s, possibly due to the ring-shaped fossils of Charniodiscus. Perhaps life in the Precambrian was recognized earlier than we think? If the third speaker, Helen Boynton, had been around 100 years ago, they surely would have been, as she has scoured almost every inch of NW Leicestershire searching for more material. The only caveat is identifying which shapes in the rocks are fossils, and which are inorganic. Going so far back in time, it's often hard to be certain.
Putting the fossils into geographical and environmental context, John Carney and Steve Noble of the British Geological Survey then explained the evidence indicating Charnwood Forest as having been part of an island arc 30'S of the Equator during the Precambrian. The closest modern analogue is probably the volcano of Montserrat, spewing out pyroclastic flows every so often, which then buried Charnia and Charniodiscus who lived a few kilometres offshore. Zircon crystals in the volcanic rocks give an age of around 562 Ma for the Charnwood creatures, but some other specimens may be as old as 611 Ma. However, the zircon crystals yielding the older ages are rather battered, suggesting they may have been re-worked.
After a coffee break, the Charnian fossils were put into a global context. Dan Condon (BGS) looked at what was going on around the world at the time - from ice ages that turned the Earth into a giant snowball to the amazing fossil embryos of the Doushantuo Formation, China. Most helpfully, there are the same chemical signals in rocks from China, Newfoundland and Oman, making correlation between regions possible.
Nick Butterfield (University of Cambridge) then gave a rip-roaring run-through of why the Ediacaran (as the period in which Charnia lived is now officially known) is such an interesting time. For thousands of millions of years there was life on Earth, but it never showed any signs of changing. Then, suddenly (geologically speaking) all sorts of things start happening, not least among the plankton. Having looked the same for an eternity, acritarchs (plankton of uncertain affinities) became spiky, suggesting that they were evolving protection against predators. Did the 'arms race' between predators and prey begin in the Ediacaran? It certainly seems possible.
|The Flinders Range, South Australia: home of the Ediacarans.|
It was time for lunch, and then Jim Gehling of the South Australian Museum told us that Leicestershire needs the deserts of the Triassic to come back as there's far too much bracken covering the place at the moment. Out in South Australia, such vegetation is pretty scarce, making Precambrian fossils much easier to find. Jim documented some new outcrops, where submarine canyons had been filled with sediment that included many Ediacaran entities.
It seems that the earliest forms lived in deep water and then diversified into shallower waters as oxygen levels increased. Bluntly, Jim then made the point that these palaeontological treasure troves deserve proper protection and conservation from the authorities. "I don't care if it's the footprints of Christ!" railed Jim: most archaeological sites are infinitely less important than these geo-localities.
Probably the best Ediacaran outcrops in the world occur in Newfoundland, and Guy Narbonne was on hand to give us a virtual tour. It would have been much cheaper to travel from Newfoundland to Charnwood during the Ediacaran, Guy pointed out, as the two regions were both part of the microcontinent of Avalonia. Since then, the Atlantic has inconveniently gotten in the way.
The Canadian fossils are thought to have lived in 100s to 1000s of metres of water, and include some very large species indeed, suggesting that there must have been some smaller, earlier forms that we simply don't know about. Then there's the mystery of how the animals grew (if they were indeed animals). Exceptional preservation of new specimens from Spaniard's Bay, Newfoundland reveals their modular construction and indicates they grew by inflation rather than the addition of segments. Ecological tiering of the fauna, suggests they were suspension feeders, but they show no affinities to extant organisms. Could they be a failed kingdom, somewhere between fungi and sponges?
|A specimen of Charnia from Newfoundland.|
The final instalment of the meeting started with Dima Grazhdankin (Dublin) discussing the ecology of different Ediacaran faunas from around the world. Charnia and its Canadian cousins lived in deep water, the Aussies liked it a bit shallower, and those from Namibia lived close to shore.
Microbial mats had a big role to play, as they held the seafloor together. There were three ways to cope with this: 1, become part of the microbial mat; 2, anchor yourself beneath a microbial mat; and 3, start moving around. Some of the Ediacarans might even have been infaunal, but this is a bit controversial.
Finally, Martin Brasier and Jonathan Antcliffe (Oxford) used lasers to get the highest resolution images of Charnia they could. They argued that Charnia didn't grow solely by inflation, as there are specimens that have too many segments - they must have added some later. They also suggested that forms of Ediacarans recognized as separate species might actually just be 'taphomorphs', or differently preserved examples of the same kind of animal.
It is possible to generate 'complex' structures using just five parameters, apparently, so many variations might just be down to how the fossils were preserved. But we still don't know how the Ediacarans functioned, nor where they fit in the tree of life. All of which means that even 50 years after Charnia was described, there's still plenty to be found out about it.