Largest ancient crab claw found on New Zealand beach

Palaeontologists have unearthed an ancient giant crab on a New Zealand beach. The extinct crustacean boasts the largest fossilised crab claw ever.

The new species of ‘Southern Giant Crab’ has the scientific name Pseudocarcinus karlraubenheimeri. It was discovered on Waitoetoe beach on New Zealand’s North Island, about 240 km south of Auckland.

Crab fossils on black background
Pseudocarcinus karlraubenheimeri fossil. Photographs: Jean-Claude Stahl (NMNZ) as in van Bakel et al.

It was found in sediment which dates to approximately 8.8 million years ago during the upper Miocene period (23–5.3 million years ago). The well-preserved specimens were found buried in a layer deposited by an ancient volcanic eruption from the offshore Mohakatino Volcanic Centre.

This volcanic region was active from about 14 to 8 million years ago.

P. karlraubenheimeri is described in a paper published in the open access New Zealand Journal of Geology and Geophysics.

The specimens would have been about 200–600 m deep in the ancient sea.

Crabs are decapod crustaceans because they have 10 limbs. Their front two limbs are chelipeds which bear “chela” – pincers or claws. Many species of crab have a larger and smaller chela.

The extinct crab from New Zealand has the largest cheliped ever found on a fossilised crab measuring about 15 cm. The authors suggest this adaptation reflects their carnivorous nature.

Among living or extinct crabs, the Tasmanian giant crab (Pseudocarcinus gigas) has the largest cheliped. The largest male claw measured 47 cm. These crustaceans can be found today across the Tasman Sea from their recently discovered ancient relatives and can reach 12 kg.

P. karlraubenheimeri may be a precursor to these colossal contemporary crabs.

Miocene conditions in New Zealand “apparently offered favourable conditions in terms of food sources, metabolic requirements, and calcium-carbonate supply” for Pseudocarcinus to grow to such large sizes, the authors write.

Recent palaeontological finds from New Zealand include the largest ever penguin – a 150 kg behemoth which lived 55 million years ago – and a 22-million-year-old dolphin which imprisoned fish with its teeth.

Adding a gigantic crab to the mix helps to further flesh out what the ancient ecosystems of New Zealand were like.

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