Quantitative imaging supports that endoskeletal mineralization in sharks is an adaptive trait.

Quantitative computed tomography across modern sharks shows endoskeletal mineralization varies strongly by species, with deeper-dwelling species generally exhibiting lower mineralization degrees.

• Why it matters: Mineralization in cartilaginous shark skeletons may reflect ecological adaptation, but it is unclear whether variation tracks evolutionary history or habitat-linked factors.
• What they did: CT imaging quantified endoskeletal mineralization in representatives from all nine shark orders spanning 26 of 35 families, then tested links to ecology versus phylogeny.
• The result: Mineralization is more closely associated with ecological factors like depth distribution than with phylogenetic relationship, supporting an adaptive role for buoyancy regulation and energy conservation.