Fossilized crustaceans linked together in head-to-tail chains recently discovered near Kunming have been recognized as the earliest form of collective behavior on Earth and an important link in the evolution of life – and have raised new questions about some of the planet's earliest life forms.
The 525 million year-old shrimplike specimens, located in the fossil-rich Chengjiang Lagerstätte roughly 50 kilometers southeast of Kunming, have been studied by a team of scientists from Yunnan University and University of Oxford and University of Leicester in the UK with their results published in the journal Science.
The Chengjiang Lagerstätte is known among paleontologists for the fossilized sea life it contains, collectively referred to as 'Chengjiang Fauna'. Chengjiang Fauna is considered one of the 'Three faunas of the evolution of early life forms' along with Burgess Shale Fauna in western Canada and the Ediacaran Fauna of South Australia.
Chengjiang Fauna centers around Maotian Mountain (帽天山) and contains numerous important discoveries, including Fuxianhuia, the ancestor of modern insects, which was discovered in 1994. It is known for its abundance of ancient arthropods, which include insects, spiders and crustaceans.
A report in The Times of London speculates on how the chain of animals was preserved so well, during the act of migration:
When they died, possibly as a result of moving into water loaded with toxins or short of oxygen, they sank to the seabed, where they were covered in sediment.
Researchers said that the migration they had embarked on could have been to reach a neighbouring area much as modern animals seek out winter feeding ground. Equally, it could have been a vertical migration, perhaps at night when the creatures may have travelled to the surface to feed in comparative safety.
How, or even if, they swam when part of a chain has mystified the Anglo-Chinese research team because none of the limbs or antenna, assuming the creatures had them, have survived the fossilisation process.
It is theorized that the animals may have simply 'surfed' currents or perhaps moved through a pulsating movement. According to Oxford professor Derek Siveter "It's still a bit of a mystery and there doesn't seem to be a direct comparison with any living animal."
Images: Nature.com
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