Elvis taxon
In paleontology, an Elvis taxon (plural Elvis taxa) is a taxon which has been misidentified as having re-emerged in the fossil record after a period of presumed extinction, but is not actually a descendant of the original taxon, instead having developed a similar morphology through convergent evolution. This implies the extinction of the original taxon is real, and one taxon containing specimens from before and after the extinction would be polyphyletic.
Etymology
The term Elvis taxon was coined by D.H. Erwin and M.L. Droser in a 1993 paper to distinguish descendant from non-descendant taxa:[1]
"Rather than continue the biblical tradition favored by Jablonski (for Lazarus taxa), we prefer a more topical approach and suggest that such taxa should be known as Elvis taxa, in recognition of the many Elvis impersonators who have appeared since the death of The King."[2]
Related but distinctive concepts
By contrast, a Lazarus taxon is one which actually is a descendant of the original taxon, and highlights missing fossil records, which may be found later.
A zombie taxon has been considered a Lazarus taxon, because it has been collected from younger stata, but later turns out to be a fossil that was freed from the original seam and was refossilized in a sediment of a younger age. For example, a trilobite that gets eroded out of its Cambrian-aged limestone matrix, and reworked into Miocene-aged siltstone.
Example
Rhaetina gregaria, one of the most common Late Triassic brachiopod species, has been regarded as a survivor that ranges across the Triassic-Jurassic boundary into the Early Jurassic. The external morphology of specimens from before and after the Triassic–Jurassic extinction event were initially regarded identical. Study of the internal features of the early Jurassic material showed it was actually quite distinct from the Triassic specimens, and should be assigned to the genus Lobothyris. Hence L. subgregaria is a well documented example of an Elvis taxon.[3]
