They called it the "goodgod" or the "Lord God bird"; folk etymology has it that when someone saw the ivory-billed woodpecker, they’d say, "Lord God, what a woodpecker." A wildlife artist named Don Eckelberry, painting one along the Tinsaw River in Louisiana in 1944, painted one and wrote he was "impressed by the majestic and wild personality of this bird." That bird, with "its vigor, its almost frantic aliveness," was the last ivory-billed woodpecker confirmed to be seen alive until this year. For sixty years, the Lord God bird was missing and presumed dead, despite occasional reports floating in of one seen here and there at a distance. They were the so-called Elvis sightings of ornithology. But years of intensive searching (combined with some good guesses on the part of the Nature Conservancy about what lands to buy in the hopes of preserving woodpecker habitat) paid off when a kayaker saw one in the Big Woods of Arkansas in 2004. Intensive video surveillance followed, confirming the bird’s presence, and this year it was announced: Elvis had not left the building. The shining beacon for cryptozoologists is the coelacanth, a fish discovered off the coast of South Africa in 1938. A South African naturalist identified it as part of an order of fishes presumed to have gone extinct some 65 million years earlier. The coelacanth seems to have a much wider range than the early rediscoverers believed, prompting cryptozoologists (who are nothing if not bold) to ask if there are previously unknown coelacanth species off the coast of Mexico. And why not? If a species as old as the dinosaurs can casually appear, if the avian Elvis can return from a sixty year intermission, if the megamouth shark can appear from nowhere and an unknown mammal species, the Laotian rock rat be discovered being served up at an outdoor market, why not assume that there are stirrings within the deep?

Pleistocene megafauna like the wooly mammoth and sabertoothed tiger survived until the rise of tool-using humans, and some may have survived even longer, until the dawn of recorded civilization. If Jurassic Park were real science, we could bring them back; but could the shadowy fragments of stories about the Nandi bear represent the Atlas bear, extinct since the Paleolithic Age? But the iconic disappearances are within more recent memory. The dodo lasted long enough for Dutch sailors to complain about the taste of "stupid bird"; there’s no particular reason why Harold Waldrop’s contribution to the world of dodo literature couldn’t be fact. The thylacine (better known as the Tasman tiger) made it longer yet, long enough to be a movie star. In his study of large predators, Monster of God, David Quammen notes that the last wild lion was seen in Iran in 1944.

The black-footed ferret is probably headed towards extinction; the species suffers from "genetic bottlenecks". But for all the talk of "mutational meltdown" and "inbreeding depression", scientists are unsure just how small a population can get before unavoidable problems begin occuring; some say that genetic bottlenecks are good. The ecosystem of which an animal was a part can disappear, and the loss of genetic diversity can mean that a species cannot cope with shocks, but a breeding population can stay alive with a surprisingly small base. The North American population of golden hamsters kept as pets are almost entirely descended from a single family of roughly a dozen animals found by a man named Aaron Abrahams in 1930.

And so why not imagine it? A lost world, be it the ocean depths or mountain fastness, with a small breeding population of something we thought we had lost. Somewhere out there, there’s a Tasmanian tiger, an Atlas bear, a passenger pigeon that survived the meatpacking plants of Chicago and Kansas City to dream of its lost billion-bird flock. There’s something to remind us that the world is stranger than we dreamed.