A CT-based comparison of 10 squalomorph shark species found a clear anatomical contrast: hexanchiform sharks have more robust inner-ear labyrinth spaces, while squaliform sharks have more slender ones. The pattern raises the possibility that ancestry helps explain shark ear shape, but the study does not show that evolution matters more than habitat or diet. Its authors say broader sampling and quantitative comparisons are needed to test those explanations.
What did scientists discover about shark ears?
Shark inner ears contribute to hearing and equilibrium. In a study published in The Anatomical Record, researchers compared the skeletal labyrinth—the space within the skull that houses inner-ear structures—in 10 living squalomorph species. Using computed tomography (CT), they described the labyrinth’s shape across the sample.
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The main reported difference was between two shark orders: hexanchiforms had more robust spaces housing the semicircular canals and ampullae, while squaliforms had more slender labyrinths. These are anatomical descriptions, not measurements of how well the sharks hear or balance.
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The researchers used CT scans to examine the structures inside shark heads. Cal Poly Humboldt described the work as digitally dissecting the heads in three dimensions. The sample included these 10 species:
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- Chlamydoselachus anguineus
- Heptranchias perlo
- Hexanchus griseus
- Notorynchus cepedianus
- Squatina californica
- Centrophorus squamosus
- Squaliolus laticaudus
- Oxynotus centrina
- Isistius brasiliensis
- Etmopterus bullisi
The paper’s publisher page provides the abstract and a data-availability statement, but not detailed scan settings or a full account of the statistical methods. The authors say supporting data are available through MorphoSource project 000450472.
Does a shark’s habitat affect its inner ear?
The 2026 comparison does not settle that question. Its sample spans different diets and habitats, and the reported order-level contrast may be consistent with a role for shared ancestry. But the authors call for broader taxonomic coverage and quantitative analysis of labyrinth geometry alongside phylogeny, locomotion and habitat. Without those tests, the observed pattern cannot establish which factors explain the differences—or whether one matters more than another.
Earlier research has reported ecological associations using other measures of elasmobranch inner ears. A 2023 MRI study examined 26 elasmobranchs and found variation associated with diet and habitat: piscivorous species had larger inner ears than non-piscivorous species, and reef-associated species had larger inner ears than oceanic species. That work measured inner-ear variation using MRI, so it is not a direct replication of the 2026 study’s CT-based comparison of skeletal labyrinth form.
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Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →A separate 2023 study examined sensory hair cells in nine shark species, rather than the gross shape of the skeletal labyrinth. It reported greater hair-cell density and total number in vertically oriented maculae among water-column feeders than among benthic feeders, while noting the limited data and need for broader study. These findings address a different anatomical level and do not determine what explains the CT study’s order-level pattern.
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What the findings do—and do not—say
| Question | What the evidence supports |
|---|---|
| Do shark inner ears differ among species? | The 2026 study describes variation in skeletal labyrinth morphology across 10 squalomorph species. |
| What contrast did it report? | More robust labyrinth spaces in the sampled hexanchiforms and more slender labyrinths in the sampled squaliforms. |
| Did it prove evolution matters more than environment? | No. The authors identify phylogeny, locomotion and habitat as factors for future quantitative analysis. |
| Does labyrinth shape predict hearing performance? | That link is not established by the accessible abstract. |
A 2016 review of fish auditory systems likewise describes broad morphological diversity and notes that the selective forces behind it, as well as the relationship between inner-ear form and hearing ability, remain open questions. The new comparison adds a useful anatomical pattern to that larger problem; it does not by itself explain the pattern’s cause.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why the study matters
The value of the work is that it documents structural diversity in a group of sharks and gives future studies a basis for testing explanations. The authors’ next-step priorities—more species, finer ecological categories, and quantitative comparisons with evolutionary history, movement and habitat—are important because related species may share features even when they occupy different environments. At the same time, previous ecological associations in other samples mean habitat should not be dismissed.
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The paper was first published on September 20, 2026. Kaci Dodd and Isamar Lopez-Argueta are joint first authors, and Allison Bronson is the corresponding author. Bronson said the findings offer a new way to investigate shark evolution and the evolution of sensory systems; that is a research direction, not a causal result demonstrated by this comparison.
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