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Ontogenetic variation in the crocodylian vestibular system
Julia A Schwab1, Mark T Young1, Stig A Walsh1,2
1School of GeoSciences, Grant Institute, University of Edinburgh, Edinburgh, UK.
Journal of Anatomy
|November 29, 2021
Summary
The inner ear vestibular system of crocodylians grows with skull size but changes shape during development. These changes are linked to skull growth constraints, not altered behaviors.
Area of Science:
- Paleontology
- Comparative Anatomy
- Evolutionary Biology
Background:
- Crocodylians inhabit tropical and subtropical regions, primarily in shallow waters.
- Ontogenetic changes in body size, skull dimensions, and bite force are observed in crocodylians, influencing prey preferences.
- While endocranial neurosensory structures change during development, the vestibular system's ontogeny remains less understood.
Purpose of the Study:
- To investigate the size and shape transformations of the crocodylian endosseous labyrinth throughout ontogeny.
- To analyze developmental changes across four distinct life stages: hatchling, juvenile, subadult, and adult.
Main Methods:
- Utilized 30 high-resolution computed tomography (CT) scans.
- Applied three-dimensional geometric morphometrics to analyze labyrinth morphology.
- Examined specimens representing four ontogenetic stages.
Main Results:
- The endosseous labyrinth increases in size during ontogeny, exhibiting negative allometry relative to skull size.
- Significant shape changes occur, with hatchlings displaying shorter semicircular canal radii and thicker diameters.
- Hatchling labyrinths are dorsoventrally shorter compared to those of mature individuals.
Conclusions:
- Ontogenetic modifications of the crocodylian labyrinth are primarily driven by skull growth constraints.
- Changes in the basicranium, such as basicranial verticalization, influence labyrinth development.
- These modifications are not directly attributed to shifts in locomotion, diet, or other functional behaviors.
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