There’s an evolutionary ‘island rule’ that says, when on an island, small animals tend to get bigger and big animals tend to get smaller. Giant bunny Nuralagus Rex* lived on the island of Minorca about 5 million years ago and was around 6-10 times larger than an average rabbit. Lack of predation allows that.
The 3 million year old Bear Otter was even more giant than todays giant otter (though there is no word on who was cuter**). Changing environmental conditions have rid us of many awesome prehistoric giants, and in the case of the bear-otter those changing conditions just might have been our own ancestors outcompeting them. Those Australopithecus afarensis jerks were meat-greedy.
But as cool as giant bunnies, otters, sloths, and even giant beavers may be, they are nothing compared to some other mammals that used to roam the earth. The largest known land mammal was the 18 ft tall 33 ft long rhino ancestor Paraceratherium. Truly dinosauric you may say. But actually there are various evolutionary limitations that put a cap on maximum mammal growth, stopping even the giants from ever truly achieving, in size, what the dinosaurs did. The mythic Amphicoelias fragillimus for example, might have reached up to 200 ft. Positively mind boggling, which is why dinosaurs will never actually go out of style, no matter how many feathers they tack on the T-rex.
This post was brought to you by Ununpentium (Uup).
*best pet rabbit name ever.
**actually scientifically speaking, the cutest otter is the Sea-otter.