RICHARD J. TWITCHETT, P. B. WIGNALL, M. J. BENTON; Discussion on Lazarus taxa and fossil abundance at times of biotic crisis Journal, Vol. 156, 1999, pp. 453–456. Journal of the Geological Society ; 157 (2): 511–512. doi: https://doi.org/10.1144/jgs.157.2.511
R. J. Twitchett writes: Palaeontologists grudgingly accept that the fossil record of most taxa is very patchy and incomplete. A particular taxon will appear in the fossil record, and then disappear for any number of millions of years, only to reappear again, apparently unchanged, in younger strata. This disappearance and reappearance is termed the Lazarus effect. Thus, in any particular interval of time a Lazarus taxon is one that is not present in the fossil record, but which we know must have existed by virtue of the presence of older and younger specimens.