Origin of placoid
Examples from the Web for placoid
The Thornback Skate is covered with prickles (placoid scales).Stories of the Universe: Animal Life|B. Lindsay
In some cases the placoid scales are enlarged to form plates or spines capped or coated with enamel.
In the groups of fishes above the Selachians, the coating of placoid elements shows various modifications.
In the Selachians the bony skeleton is restricted to the placoid elements.
The teeth of Selachii are fundamentally identical with placoid scales.