Development of cycloid or ctenoid scales
1. Dermal cells accumulate and form scleroblasts
2. Scleroblasts arrange into a dermal papilla
3. Dermal papilla pushes the epidermis and secretes bone to form the scale rudiment
4. Scale increases in thickness and dimension as more bone is secreted
5. Anterior edge grows inward, posterior edge grows outward pushing the epidermis
6. Epidermis either remains as a thin membrane or ruptures leaving the posterior edges exposed
7. The bony scale is entirely dermal in origin