Pristification: Defining the convergent evolution of saws in sharks and rays (Chondrichthyes, Neoselachii)

Abstract

Convergent evolution is the development of analogous structures or bauplans in at least two independent lineages of organisms. Convergence is driven by the occupation of similar ecological niches and by various physical and phylogenetic constraints (McGhee, 2011). Despite the wide recognition of this phenomenon in evolutionary biology, formal terms and definitions for specific examples are rare. The most notable is carcinisation, which refers to the appearances of a crab-like bauplan among crustaceans (Keiler et al., 2017). Here the term ‘pristification’ is proposed for the convergence of saws in sharks and rays. It was coined previously in a preliminary publication (Greenfield, 2021a) but is formally defined for the first time. Not only does it highlight a remarkable convergent structure, but it also serves as a template for future terminology.