“…During ontogeny, most vertebrate skeletons are initially composed predominantly of hyaline cartilage and largely replaced by bone via endochondral ossification (Hall, 1975(Hall, , 2005. In contrast, chondrichthyans, including elasmobranchs (sharks, skates, rays, and relatives) and holocephalans (chimaeroids) do not develop osseous skeletons, having secondarily lost the ability to produce endoskeletal bone (Coates et al, 1998;Dean and Summers, 2006;Ryll et al, 2014;Debiais-Thibaud, 2019;Brazeau et al, 2020). Instead, the chondrichthyan endoskeleton remains primarily composed of hyaline-like cartilage, with elasmobranchs developing a comparatively thin outer layer of cortical mineralization over most of their skeleton during ontogeny (Hall, 2005;Egerbacher et al, 2006;Dean et al, 2009Dean et al, , 2015Seidel et al, 2016Seidel et al, , 2019bAtake et al, 2019;Debiais-Thibaud, 2019).…”