A new shark inner ear study that used CT scans of 10 species found that the bony chambers housing the ear vary widely in shape, and the differences may reflect evolutionary history more than diet or habitat, according to researchers at Cal Poly Humboldt.
The team expected ecology to shape the ears, as it has in some other vertebrate groups. Instead, sharks with similar diets and habitats turned out to have very different ear shapes, according to the university’s release on the work.
What the researchers did
The paper, “Comparative morphology of the skeletal labyrinth in extant squalomorph sharks,” appeared online in The Anatomical Record on Sept. 20, 2026 (read the peer-reviewed study). Kaci Dodd and Isamar Lopez-Argueta are joint first authors, and Allison Bronson is the corresponding author. The university says the project was led by the two students and Bronson, a professor.
The skeletal labyrinth is the bony space that houses the membranous labyrinth, the soft structure of the ear. CT scanning let the team assess those spaces in three dimensions across squalomorphs, one of the two primary clades of elasmobranchs, the group that includes sharks, rays and skates.
The 10 species examined were:
- frilled shark (Chlamydoselachus anguineus)
- sharpnose sevengill shark (Heptranchias perlo)
- bluntnose sixgill shark (Hexanchus griseus)
- broadnose sevengill shark (Notorynchus cepedianus)
- Pacific angelshark (Squatina californica)
- leafscale gulper shark (Centrophorus squamosus)
- spined pygmy shark (Squaliolus laticaudus)
- angular roughshark (Oxynotus centrina)
- cookiecutter shark (Isistius brasiliensis)
- lined lanternshark (Etmopterus bullisi)
Relatedness over lifestyle
The release says closely related sharks had similar inner ears even when they lived in different environments. That points to evolutionary history as a stronger influence on ear structure, though the researchers frame it as a possibility rather than a settled conclusion.
AOL, in its coverage of the study, reported that hexanchiform sharks, the sixgill and sevengill group, had sturdier labyrinth spaces, while squaliform sharks had slimmer ones. Sharkophile could not check that detail against the full paper.
The findings also apply only to squalomorphs. The other main elasmobranch clade was not part of this work, so the results do not describe sharks as a whole.
Where this fits
Earlier work has pointed the other way. An MRI study of 26 elasmobranch species reported inner ear variation influenced by diet and habitat, with fish-eaters having larger inner ears and reef species having larger ears than oceanic ones. That study used different methods and a different sample, so it does not directly contradict the new paper.
Shark anatomy and evolution are a recurring subject here; see our earlier story on the evolution of shark jaws.
AOL reported that the specimens came from the Cal Poly Humboldt Fish Collection and museums around the world, and that the work shows how useful publicly available specimen data can be for studying how shark senses evolved.
Source: AOL.com, Cal Poly Humboldt, Phys.org / Study: PubMed Central
