Keel
Definition
The keel is an enlarged ridge on the sternum (breastbone) that anchors the powerful pectoral muscles penguins use for swimming. In flying birds the keel supports flight muscles, but in penguins the same structure has been repurposed for aquatic locomotion. A penguin's keel is proportionally larger than in many flying seabirds because the pectoral muscles must generate enough thrust to propel a dense, streamlined body through water. This skeletal feature is a key piece of evidence that penguins descended from flying ancestors.
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Frequently Asked Questions
What does keel mean in penguin biology?
The keel is an enlarged ridge on the sternum (breastbone) that anchors the powerful pectoral muscles penguins use for swimming. In flying birds the keel supports flight muscles, but in penguins the same structure has been repurposed for aquatic locomotion. A penguin's keel is proportionally larger than in many flying seabirds because the pectoral muscles must generate enough thrust to propel a dense, streamlined body through water. This skeletal feature is a key piece of evidence that penguins descended from flying ancestors.
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Glossary entries define the language. FAQ answers common questions; guides carry the longer Survival Lab arguments.
More in anatomyWhere this definition comes from
Reference bodies behind the anatomy terminology. Links last checked August 5, 2026.
- Smithsonian Ocean Portal - Penguin biology, anatomy, and breeding explainers.
- British Antarctic Survey - Antarctic penguin ecology, diving, and sea-ice context.
- Australian Museum - Little penguin biology and coastal breeding behavior.