A team of paleontologists led by Joern Hurum of the University of Oslos Natural History Museum last year excavated the skeleton of an enormous 150-million-year-old pliosaur; after months of piecing bones together, they now are confident it is largest of its kind ever discovered. Typical pliosaurs—tear-shaped swimmers with short necks—were about 20 feet long, but the paleontologists guess that this monster stretched to some 50 feet in length.