Giant claw reveals the largest ever arthropod. 2007. S.J. Braddy, et al. Biology Letters, published on-line Nov. 20, 2007.
From National Geographic News:
Jaekelopterus rhenaniae measured some 2.5 meters long, scientists estimate, based on the length of its 46-centimeter, spiked claw. The 390-million-year-old sea scorpion was the top predator of its day, slicing up fish and cannibalizing its own kind in coastal swamp waters, fossil experts say.
Smaller sea scorpions are known to have crawled ashore to mate or shed their outer skins. But "there's no way this monster bug would have been able to do that, because it was just too big," Braddy said.
"Its legs were relatively flimsy compared to the size of its body," he added. Without water buoying the big beast up, its legs would have collapsed under the weight of its body, Braddy said.