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Fossil shells reveal how ancient animals survived global warming
Ancient marine fossils are providing new insights into Earth's biggest mass extinction.
Researchers discovered exceptionally well-preserved animals that lived in the aftermath of Earth's most catastrophic mass extinction event, 252 million years ago.
The extinction profoundly affected life on Earth, wiping out as many as 95% of species that leave a fossil record. A period of extreme global warming was followed by a time of little diversity of life.
Newly discovered fossilised shellfish have helped researchers understand how marine ecosystems recovered from this period of change.
A team led by Museum scientists found the specimens in Spitsbergen in Arctic Norway. They suggest that the ocean in this area was far from empty - it supported an unexpectedly diverse animal community just after the extinction.
Its animals managed to thrive when global temperatures were at their hottest.
The team searched for fossils in Spitsbergen in Norway
Professor Richard Twitchett, a Museum palaeontologist who studied the shells, says, 'Finding these beautiful little fossils was completely unexpected and yet they have transformed our understanding of this important time in Earth's history.
'They show us that the temperate areas of the world, where Spitsbergen was at the time, acted both as a refuge during extreme extinction and global warming, and as a cradle of evolution for the ancestors of some species that are still alive today.'
Tiny shells give huge insights
The team collected the fossils from a remote site in the Arctic, but it was only once back at the Museum that they realised the full extent of their discovery.
Many of the fossil shells are unusually small, only a few millimetres in size. But they are so well preserved that they reveal new details of their body shape and early life stages.
These details show that some species thought to be extinct had actually survived the extinction, and others originated tens of millions of years earlier than previously believed.
Dr William Foster from the University of Texas and Dr Silvia Danise from the University of Georgia also worked on the study, which is published in the Journal of Systematic Palaeontology.
Dr Foster says, 'The exceptional preservation of the fossil shells show how marine ecosystems survive global warming.
'They reveal that animals that release their larvae into the water column appear to have had a greater likelihood of survival and recovery.'
The struggle to find oxygen
During periods of global warming, the sea floor would have held very little oxygen - not enough to support animal life.
Some of the fossils as they were found in the field
Larvae released into water would have floated near the surface, which had more oxygen, and could have travelled further. This allowed the young animals to find patches of sea floor that were better able to support them.
Even the smallest, thinnest shells in the study are undamaged. This shows the seawater in which these animals lived and reproduced was not affected by ocean acidification.
Protecting future ecosystems
Today, global warming and pollution are causing major environmental stress to marine ecosystems.
Studying how ancient marine animals responded to past changes can provide valuable insights into how they may respond to warming seas in the future. It can also help scientists identify what traits may be important for survival.
Dr Silvia Danise says, 'This discovery reminds us that there is still much to learn about the impact of past episodes of global warming on the evolution of marine ecosystems.
'Our research is showing how environmental changes affected different animal groups and how similar responses are recorded during different episodes of past change. We can tell a lot from well preserved fossils.'
