How can you tell that a bony fish is not cartilaginous fish?

There are several key differences between bony fish and cartilaginous fish that can be used to distinguish them.

1. Skeleton: Bony fish have a skeleton made of bone, while cartilaginous fish have a skeleton made of cartilage. Cartilage is a flexible, non-mineralized connective tissue, while bone is a hard, mineralized tissue.

2. Scales: Bony fish have scales that are made of bone or modified bone, while cartilaginous fish have scales that are made of a material called placoid. Placoid scales are small, tooth-like structures that are embedded in the skin.

3. Fins: Bony fish have fins that are supported by bony rays, while cartilaginous fish have fins that are supported by cartilaginous rays.

4. Gills: Bony fish have gills that are covered by a bony operculum, while cartilaginous fish have gills that are not covered by an operculum.

5. Teeth: Bony fish have teeth that are located in their jaws, while cartilaginous fish have teeth that are located on their jaws and gill arches.

6. Eyes: Bony fish have eyes that are located on the sides of their head, while cartilaginous fish have eyes that are located on the top of their head.

7. Nostril: Bony fish have two nostrils, while cartilaginous fish have one nostril.

8. Spiracles: Bony fish do not have spiracles, while cartilaginous fish have spiracles which are small openings on the top of their head that allow water to flow into their gills.

9. Caudal fin (tailfin): Bony fish have a caudal fin that is symmetrical, meaning it is the same shape on both sides, while cartilaginous fish have a caudal fin that is asymmetrical, meaning it is different shapes on both sides.