Fossil Hunter Discovers Gigantic Crab in New Zealand—a New, Extinct Species

The massive creature is 8.8 million years old, and its modern descendants in Australia can grow to be the weight of a human toddler

Close-up of fossilized crab claw embedded in a rock
P. karlraubenheimeri lived during the Miocene Epoch roughly 8.8 million years ago. Van Bakel and Ossó / New Zealand Journal of Geology and Geophysics 2024

In 2008, amateur fossil hunter Karl Raubenheimer was walking near his home in Taranaki, New Zealand, when he spotted a huge claw poking out from a rock. Upon closer inspection, he realized the pincer was attached a massive, perfectly preserved crab.

Raubenheimer, a musician who also runs a fossil-themed YouTube channel, kept scouring the coastline, and ten years later, he found another, similarly intact, enormous crab. He decided to donate both to the Museum of New Zealand Te Papa Tongarewa.

Now, researchers report in the New Zealand Journal of Geology and Geophysics that Raubenheimer stumbled upon an entirely new species of crab with these two finds. They’ve named it Pseudocarcinus karlraubenheimeri in his honor.

“This is the largest fossil crab to have ever been discovered, which is fascinating,” says study co-author Barry W. M. van Bakel, a paleontologist at Utrecht University in the Netherlands, to IFLScience’s Rachael Funnell.

P. karlraubenheimeri lived during the Miocene Epoch roughly 8.8 million years ago, alongside other species of big and small crabs. The larger of Raubenheimer’s fossils had a body, or carapace, that measured eight inches across; it also had a massive, eight-inch long claw, reports Scientific American’s Kate Evans.

These crabs likely lived in waters that stretched several hundred meters deep, where scientists suspect they feasted on other crustaceans, clams and snails. They, in turn, were a source of food for ancient seals, whales and dolphins.

The fossilized crabs likely died as a result of—and were subsequently preserved by—an eruption of the nearby Mohakatino Volcanic Center. At the time, the region was a hotbed of volcanic activity, with gases from underwater vents adding nutrients to the water.

Fossilized crabs in rock
P. karlraubenheimeri likely lived deep underwater. Van Bakel and Ossó / New Zealand Journal of Geology and Geophysics 2024

“Taranaki around the Miocene into Pliocene era had this really rich biodiversity in the seas and on shore,” says Nic Rawlence, a paleogeneticist at the University of Otago, to Stuff’s Catherine Groenestein. “This discovery and others in Taranaki have shown us what was here in Taranaki during this time, it is truly a lost ecosystem.”

Though P. karlraubenheimeri is extinct, its descendants live on today: Pseudocarcinus gigas, also known as southern giant crabs or Tasmanian giant crabs, are this ancient creature’s modern relatives. These crabs of today are even larger than P. karlraubenheimeri, with claws that can grow up to 20 inches long. They can weigh up to 37 pounds—as much as a human toddler.

Commercial fishers make their living catching southern giant crabs off the coast of Tasmania in Australia. However, the creatures don’t have an established population in the waters around New Zealand, located some 1,500 miles to the east. The new finds are the first recorded evidence that Pseudocarcinus crabs inhabited the area that is now New Zealand.

The crustaceans’ evolutionary backstory has largely been a mystery to scientists—until now. The newly discovered species will likely help fill in some of the blanks about how southern giant crabs came to be.

“Gigantic or not, crabs are a spectacular example of the complexities of evolution,” says Javier Luque, a researcher at the University of Cambridge in England who was not involved with the new paper, to Scientific American. “They have an astonishing diversity of form and function. And in order to make sense of that current diversity, we need to take a glimpse into the past.”

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