noun
- Plural of placoid; fish scales that are small, hard, and tooth-like, found on sharks and rays.
Usage: technical; zoology
Examples
- Sharks are covered with placoids that reduce drag as they swim through water.
- The placoids on a ray's skin are similar in structure to teeth.
- Unlike cycloid scales found on most fish, placoids are rigid and pointed.
- Marine biologists study placoids to understand how sharks evolved their unique skin texture.
- The arrangement of placoids helps sharks move more efficiently through the ocean.