As every schoolboy knows, Sir Arthur Conan Doyle's 1912 novel, The Lost World was inspired by the tepuis: the 100-odd mesas towering on perpendicular cliffs up to a mile above the jungle in the borderland of Guyana and Venezuela. Of course, even as a schoolboy, when I read the novel (twice), I sensed a problem: huge animals require lots of living room, and a "plateau" only 20 miles wide was far too small for a breeding population of even a single species of dinosaur. No, dinosaurs do not, and cannot, inhabit the cloud-masked, rain-soaked, infertile tops of the tepuis. But that does not mean they are not ecological islands, with populations isolated one from the other and undergoing divergent evolution. You cannot throw a net in this jungle without finding a species of something or other unknown to science. Therefore, we should take seriously any account of unknown species somewhat larger than the run-of-of-mill.