An illustration of Anomalocaris canadensis, a fearsome Cambrian predator (Picture: Katrina Kenny/SWNS)
Half a billion years ago, a huge shrimp roamed the seas.
Three foot long and with bulging eyes on stalks, the early giant has long been thought as an apex predator, responsible for the scarred and crushed fossilised remains of trilobites unfortunate enough to cross its path.
However, a new study argues that Anomalocaris canadensis – which essentially translates as ‘weird shrimp from Canada’ – was not as tough as first thought, only targeting soft, squishy prey with its fearsome-looking appendages.
A global team of researchers created a 3D reconstruction of canadensis and its two front ‘claws’ from extraordinarily well-preserved – but flattened – fossils dug up from Canada’s Burgess Shale.
Using modern whip scorpions and whip spiders as models – both of which have similar appendages – the team believes that while the shrimp was able to use them to stretch out and grab prey, they would not have been strong enough to crush whatever was on the menu.
Reflecting on the idea that canadensis feasted on tough trilobites, lead author Dr Russell Bicknell, of the American Museum of Natural History, said: ‘That didn’t sit right with me, because trilobites have a very strong exoskeleton, which they essentially make out of rock, while this animal would have mostly been soft and squishy.’
A pair of fossilised Anomalocaris canadensis appendages (Picture: Alison Daley/SWNS)
Soft and squishy, but also fast.
During the course of their research, published in Proceedings of the Royal Society B Biological Sciences, the team used computational fluid dynamics to place the 3D model in a virtual current. This helped predict what body position it would likely use while swimming.
The results suggest canadensis was likely a speedy swimmer, zooming after soft prey with its front appendages outstretched.
A close-up of the head of a complete specimen of Anomalocaris canadensis from the Cambrian Burgess Shale of Canada, showing a flexed frontal appendage (Picture: Alison Daley/SWNS)
The giant shrimp lived during the ‘Cambrian explosion’, a time when life on Earth was rapidly expanding and most major animal groups started to appear.
However, it seems they weren’t all there for the picking by canadensis.
‘Previous conceptions were that these animals would have seen the Burgess Shale fauna as a smorgasbord, going after anything they wanted to, but we’re finding that the dynamics of the Cambrian food webs were likely much more complex than we once thought,’ said Dr Bicknell.
The question is now – what did crush the trilobites?
Its name literally means ‘odd shrimp from Canada’.