Intraspecific variation in semicircular canal morphology-A missing element in adaptive scenarios?

Journal Article (Journal Article)


Recent evidence suggests that the amount of intraspecific variation in semicircular canal morphology may, itself, be evidence for varying levels of selection related to locomotor demands. To determine the extent of this phenomenon across taxa, we expand upon previous work by examining intraspecific variation in canal radii and canal orthogonality in a broad sample of strepsirrhine and platyrrhine primates. Patterns of interspecific variation are re-examined in light of intraspecific variation to better understand the resolution at which locomotion can be reconstructed from single individuals.

Materials and methods

Data was collected from high-resolution CT scans of 14 size-matched, related species. Six of these taxa have existing data on rotational head speeds.


The level of intraspecific variation was found to differ in strepsirrhine and in platyrrhine species pairs, with larger ranges of variation generally observed for the slower moving taxon than the faster moving one. Taxa that are classified as relatively agile can to some extent be separated from those who are slower-moving, but only when comparing similarly sized, closely related species with more extreme forms of locomotion.


Our findings agree with previous research showing that canal intraspecific variation can fluctuate according to species-specific locomotor behavior and extends this further by identifying behaviors that may be under unusual selective pressure. It also demonstrates the complexity of interpreting inner ear morphology in the context of broadly applicable locomotor "categories" of the kind commonly used in behavioral studies. We suspect that simplified models predicting vestibular sensitivity may be unable to differentiate behaviors when only a single specimen is available.

Full Text

Duke Authors

Cited Authors

  • Gonzales, LA; Malinzak, MD; Kay, RF

Published Date

  • January 2019

Published In

Volume / Issue

  • 168 / 1

Start / End Page

  • 10 - 24

PubMed ID

  • 30408143

Electronic International Standard Serial Number (EISSN)

  • 1096-8644

International Standard Serial Number (ISSN)

  • 0002-9483

Digital Object Identifier (DOI)

  • 10.1002/ajpa.23692


  • eng