| 1. | Chondrichthyes have a bony skeleton, while Osteichthyes have a cartilaginous skeleton. |
| 2. | Chondrichthyes are primarily freshwater fish, while Osteichthyes are mainly marine. |
| 3. | Chondrichthyes have an operculum covering the gills, while Osteichthyes do not. |
| 4. | Chondrichthyes have a cartilaginous skeleton, while Osteichthyes have a bony skeleton. |