If anyone ever challenges you to name an animal that's as awkward as it is terrifying, calmly reply, "duh, the Therizinosaurus." This late Cretaceous therapod was several meters tall and sported 40-inch claws, the biggest of any animal ever. It also had a weird pot belly, a snubbed tail, and a beaky face: behold, the strangest Frankenstein monster in existence. It's so bizarre that at first, paleontologists didn't even believe its fossils belonged together. Artwork by IsisMasshiro.