Cosmoid scales

Cosmoid scales are found in the Lungfishes (family Ceratodidae) and some fossil fishes.

Australian Lungfish scale

Australian Lungfish scale
Photographer: Carl Bento © Australian Museum

Cosmoid scales are similar to placoid scales and probably evolved from the fusion of placoid scales. They consist of two basal layers of bone, a layer of dentine-like cosmine, and an outer layer of vitrodentine.

As the fish grows each scale becomes larger as new bone is added to the basal layers.

Helfman, G.S., Collette, B.B. & D.E. Facey. 1997. The Diversity of Fishes. Blackwell Science. Pp. 528.

Mark McGrouther , Collection Manager, Ichthyology
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Tags fishes, ichthyology, cosmoid scales, Australian Lungfish,