This remarkable fossil shows an extremely rare example of fossilised collective behaviour, with shrimp-like beasties joined in a chain.

Although there are no modern analogues for this behaviour Derek Siveter of the University of Oxford thinks it might be some kind of migration.

“The spiny lobster is one example of this sort of migratory behaviour amongst modern arthropods,” he says (press release). “These lobsters join together in a kind of ‘train’ with the antennae of one animal sometimes touching the tail of the animal in front. However, the animals represented by the Chinese fossils are much more closely interlocked – they formed ‘chains’ rather than ‘trains’.”

The chains could also feasibly be some phase in the reproductive process or a peculiar life cycle stage. Or maybe they’re just having a conga line party.

“It’s still a bit of a mystery and there doesn’t seem to be a direct comparison with any living animal,” says Siveter (The Times).

The fossil was found in China and a paper detailing the results are published this week in Science by researchers from Oxford, Leicester and Yunnan.