Crushing it

Sixteen years ago, teenage fossil-fossicker Karl Raubenheimer was scouring a beach at Waitoetoe near his home in Taranaki when he spotted a boulder with something strange sticking out. It was a fossilised crab claw, a truly humongous one. Using pneumatic air scribes and grinders, Raubenheimer cracked the stone open and a familiar shape—a huge male crab, in remarkable condition—began to emerge. Raubenheimer sent photographs of the find, as well as five further crab fossils from the same area, to Barry van Bakel, a palaeontologist and crab expert in the Netherlands, and Àlex Ossó, a palaeocarcinologist from Spain. The pair confirmed that the 15-centimetre appendage was the largest ever found in fossil form—and that it was attached to an extinct but new-to-science species, which they named after its finder: Pseudocarcinus karlraubenheimeri. “So that’s pretty cool,” Raubenheimer said to 1 News. Size matters, in the animal kingdom. Only the males sported the single, enlarged claw, which van Bakel said was used for crushing the shells of prey and as a “sexual show-off”. That first claw Raubenheimer found is a considerable piece of hardware. But, according to van Bakel, fossil fragments from the same area suggest the species could get even bigger, with claws up to 20 centimetres. In a recent paper, van Bakel describes the literal arms race between shell-crushing crabs and their gastropod prey. The crab’s large weaponry is “significantly expensive”  to build and maintain, he says. But it’s energy well spent: the myriad spikes and grooves on a crab’s claw are not random, but the result of an ongoing effort to build the perfect crushing apparatus. This contest is very much alive today. The giant southern crab (Pseudocarcinus gigas), likely descended from the species Raubenheimer discovered, can still be found scouring the deep waters off the Australian coast. And P. karlraubenheimeri would be proud of its progeny: at a staggering 47 centimetres long, P. gigas (pictured) holds the record for largest crab claw ever. The largest males can weigh as much as 12 kilos. It’s this mammoth size that often lands P. gigas in hot water—usually before being served as a meal. Strict quota limits are in place to maintain populations of the slow-growing crustacean, which are exported live to China and can sell for more than $200 per kilo. Van Bakel understands the appeal. The extinct crab, likewise, he says, was “large, with a lot of muscles and meat. It would have made a great dinner.”



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