Size and Weight:
Just how big was Nuralagus? Well, the full name of this megafauna mammal is Nuralagus rex--which translates, roughly, as Rabbit King of Minorca, and not incidentally makes a sly reference to the much, much bigger Tyrannosaurus rex. The fact is that this prehistoric rabbit weighed over five times as much as any species living today; the single fossil specimen points to an individual of at least 25 pounds. Nuralagus was very different from modern rabbits in other ways besides its enormous size: it was unable to hop, for example, and it seems to have possessed fairly small ears.
Nuralagus is a good example of what paleontologists call "insular gigantism": small animals restricted to island habitats, in the absence of any natural predators, have a tendency to evolve to larger-than-usual sizes. (In fact, Nuralagus was so secure in its Minorcan paradise that it actually had smaller-than-usual eyes and ears!) This is distinct from an opposite trend, "insular dwarfism," in which large animals confined to small islands tend to evolve to smaller sizes: witness the petite sauropod dinosaur Europasaurus, which "only" weighed about a ton.