An Elvis taxon is a species or higher group that has been misidentified as reappearing after presumed extinction. These examples may appear to have some similarities with older and/or extinct species—but unlike other living fossils are not actual descendants of them. The similarities are just coincidental, most likely due to convergent evolution, making the Elvis taxon polyphyletic with its extinct "ancestor".
The term comes from Elvis Presley, and references the countless Elvis impersonators that have cropped up since his death. They may look like Elvis, but they're not actually related to him.