Jigsaw complete for ancient predator

For an animal nicknamed the "T. rex of the Cambrian" – the apex predator of its food chain – the ancient arthropod Hurdia victoria has had a tough time getting properly recognised.

The species was initially described as a crustacean by American palaeontologist Charles Walcott in 1912. But its bizarre appearance and the discovery of numerous partial fossils led to it being misclassified variously as a species of jellyfish, sea cucumber and its close relative Anomalocaris.

Now a new analysis of numerous Hurdia fossils – including the animal's whale-like carapace – suggests that all these specimens belong to a single species.

"The animal is very strange looking," says Allison Daley, a palaeontologist at Uppsala University in Sweden, who led the new classification.

She says the early arthropod may have grown to be half a metre long and sat near the top of its marine food chain, some 500 million years ago.

Hurdia is among the most abundant predators in a western Canadian rock formation called the Burgess shale. Study co-author Jean-Bernard Caron, an invertebrate palaeontologist at the Royal Ontario Museum in Toronto, says that Hurdia probably skulked around the bottom of the ocean in large numbers.