In defense of living fossils

Lately there has been a wave of criticism of the concept of living fossils. First, recent research has challenged the status of paradigmatic living fossil taxa, such as coelacanths, cycads, and tuataras. Critics have also complained that the living fossil concept is vague and/or ambiguous, and that it is responsible for misconceptions about evolution. This paper defends a particular phylogenetic conception of living fossils, or taxa that (a) exhibit deep prehistoric morphological stability; (b) contain few extant species; and (c) make a high contribution to phylogenetic diversity. The paper shows how this conception of living fossils can make sense of recent research on contested cases. The phylogenetic living fossil concept has both theoretical and practical importance: theoretical, because it picks out an important explanatory target for evolutionary theory; and practical, because it picks out taxa that we might wish to prioritize for conservation. The best way to defend the concept of living fossils is to get clearer about the reasons for defending living fossil taxa.