During the Cambrian period, some 500 million years ago, the peak ocean predators were members of a group of invertebrates known as Radiodonta – arthropods with a lot of teeth and which could grow up to a metre long.
Full-grown specimens were clearly dangerous creatures, but now new research reveals their newborns were also far from harmless.
Writing in the journal National Science Review, a team of palaeontologists led by Jianni Liu from China’s Northwest University describes the first juvenile radiodontan ever found – and, size notwithstanding, it turns out to be one scary beast.
Liu and his colleagues reveal a creature that was only 18 millimetres long when it perished. A member of the radiodontan species Lyrarapax unguispinus, the specimen was an “instar” – a juvenile arthropod between moults.
Don’t go assuming that a baby radiodonton was, in the manner of a baby wolf or a baby lion, bug-eyed and cute, yet to develop the impressive predatory weaponry of its parents. Juvenile L. unguispinus came complete with all adult accessories, including spiny grasping appendages and a full complement of teeth.
The evidence, writes Liu and his team, shows that the species “was a well-equipped predator at an early developmental stage”.
This in turn indicates that raptorial feeding – that is, securing prey by violent means – was an early evolutionary development, in place by half a billion years ago.
This latest piece of fossil evidence adds weight to the theory that predation was a major factor in fuelling the evolutionary arms race that became known as the Cambrian Explosion.
Andrew Masterson is a former editor of Cosmos.
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