Fossils Reveal the Lightweight Skeletons of Sharks may have Evolved from Heavy Skeletons of Bony Fish
Sharks were thought to have evolved with a cartilage-based skeleton before other types of fish formed a bony skeleton, but a 410-million-year-old fossil fish, Minjinia turgenensis, found in Mongolia suggests the reverse—the lighter skeletons of sharks may have evolved from bony ancestors, rather than the other way around.
Brazeau MD, Giles S, Dearden RP et al. (2020) Endochondral bone in an Early Devonian ‘placoderm’ from Mongolia. Nat Ecol Evol [published online ahead of print]. https://doi.org/10.1038/s41559-020-01290-2