Amphicoelias (meaning "Double Hollow Biconcave") is a genus of sauropod dinosaur from Late Jurassic Colorado. It was discovered by Edward Drinker Cope in December 1877. It was found during the Bone Wars. There are three species, but only two are valid, the third species is a mix of one Amphiocoelias species with other diplodocid dinosaurs. The second species, A. fragillimus, was discovered by Oramel Lucas in 1877, as well. It might have been the largest dinosaur ever. It was longer than Diplodocus and Supersaurus, it was taller than Sauroposeidon. It's bones were "misplaced" (despite their enormous size). Every attept to finding these bones were in vain.

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