A snapshot of life 560 million years ago

Casts of a group of fossils that have puzzled palaeontologists for at least 60 years will go on display at the Sedgwick Museum of Earth Sciences in Cambridge today. The temporary exhibition – ‘Ediacaran Enigmas: Resolving the Fossil Record of Early Animals’ – showcases current research into life on Earth between 560 and 580 million years ago.

The casts have been taken from impressions of fossils from the Ediacaran, a geological period formally ratified by the world’s scientists only ten years ago.  The fossils – which some researchers suggest could be some of the earliest examples of animals – predate those from the Cambrian by around 40 million years.

The 15 examples of Ediacaran fossils on display in the exhibition date from a period when scientists believe that multicellular life on Earth was in the process of diverging into the major groups, or Kingdoms (such as fungi and animals) that we are familiar with today.  Many of the fossils have not been shown in the UK before, and the display is the first research-based exhibition of Ediacaran material to be staged in the UK.

Twelve of the casts on display are of fossils found in the dramatic cliffs of Mistaken Point on the east coast of Newfoundland. “The fossils seen on bedding planes [sheets of rock] at Mistaken Point are quite literally a snapshot of an ancient community – they capture a wide range of life-forms as they appeared at a particular moment in geological time,” said palaeontologist Dr Alex Liu, who has coordinated the exhibition with colleagues at the Department of Earth Sciences.

The remaining three casts on show are of fossils from Charnwood in Leicestershire, including a cast of the iconic Ediacaran organism Charnia masoni, found by a schoolboy in 1957. Strange impressions had been recognised in Charnwood as long ago as 1848, but it was only with the 1957 discovery that their importance as true Precambrian fossils was realised. Similar fossils have since been found in Russia, Namibia and Australia, revealing that these organisms were widespread on the planet during Ediacaran time. 

“When David Attenborough released a television documentary called ‘First Life’ about the Ediacaran biota in 2010, it sparked huge public interest in this time period,” said Liu. “We’re now working to find more, better-preserved material and to use the latest analytical techniques to discover new insights about the environments and organisms living during this fascinating interval.”

Mistaken Point, which may soon become a World Heritage Site, was first discovered by scientists in 1967. Liu has visited the site (so called because ships often foundered there having mistaken it for Cape Race to the east) each year since 2007. Jutting out into the Atlantic and often swathed in fog, its cliffs are rich in fossils – so rich that some planes contain as many as 4,000 specimens.

“These fossils can be interpreted as a single community, enabling researchers to look at aspects of their lifestyles including competition, feeding and reproduction. We can identify at least 22 different species of organism, many of which were anchored to the sediment with their fronds elevated into the water column,” said Liu.

With permission from the Parks and Natural Areas Division, Government of Newfoundland and Labrador, Liu took ‘peels’ (silicon rubber impressions) of the fossils in situ.  To reach the site means a two-hour drive from the city of St John’s, a 40-minute journey along bumpy tracks, and then a 45-minute trek on foot across rough terrain.

Back in Cambridge, the peels are used by Liu and colleagues to make solid casts which, once painted, closely resemble the original rocky material. These casts are essentially replicas of impressions left in the rocks by organisms whose shapes resemble the fronds of modern ferns. The largest cast on display is of an organism almost 60 cm in diameter. The smallest is a 20 mm-long fossil of a Charnia.

The bedding planes from which these fossils originate offer precious clues about early life forms. Canadian palaeontologists working on the material from Mistaken Point favour the argument that they are examples of early stem group animals, from which the major groups of modern animals – such as molluscs, cnidarians and sponges – evolved. Others suggest that they are a “failed evolutionary experiment” in multicellular life that has subsequently gone extinct.

Liu said: “The big question is whether we can find convincing evidence for the presence of features in these fossils that can conclusively determine their biological relationships. In the past, study of their overall structure has not revealed many useful features, so by applying modern techniques, and considering evidence for how they might have been behaving – in terms of feeding, movement, or reproduction – we are hoping that we can determine exactly what these organisms were.”

He and his colleagues hope that the display will raise awareness of the fascinating research going on to establish more about these fossils and others from the same period. A slideshow accompanying the exhibition shows some of the field sites, the techniques used to study the fossils, and a virtual reconstruction of these ancient ecosystems.

“The casts enable us to look in detail at the fossils, and to determine their fine morphological structure,” said Liu. “Many of the impressions in the rock are low relief, which means that they are hard to spot except when the sun is low in the sky. In the laboratory we can control the lighting so that we can see them in all their glory. The way we have lit them in the display cases should show how important this is.”

The exhibition, ‘Ediacaran Enigmas: Resolving the Fossil Record of Early Animals’, runs until December 2014. The Sedgwick Museum of Earth Sciences is open to the public Monday to Saturday. For opening hours and all other information go to http://www.sedgwickmuseum.org/

For more information about this story contact Alexandra Buxton, Communications Office, University of Cambridge, amb206@admin.cam.ac.uk 01223 761673.

Inset images top and bottom: Mistaken Point, Newfoundland (Jack Matthews). Images centre: fossils from the famous fossil-bearing surfaces (Alex Liu)