Give one example each for an animal possessing placoid scales and that with cycloid scales.
Fishes possess dermal scales, each scale made of dentine that is secreted by dermal papilla. Placoid scales are hard and microscopic in size, their body is made up of dentine and exposed surface is covered with enamel, Cyctoid scales are strong and extremely flexible.
They are large, oval and madeup of isopectine (layer of collagenousfibre). Placoid Scales are the characteristic features of cartilaginous fishes. (e.g., Scoliodon). Whereas, cycloid scale are found in bonyfishes (e.g., Catlacatla)
