What is the difference bony fish and cartilaginous jawless fish?

Bony fish and cartilaginous jawless fish are two distinct groups of fish that exhibit significant differences in their skeletal structures, jaw anatomy, and overall morphology. Here are some key differences between bony fish and cartilaginous jawless fish:

1. Skeletal Structure:

- Bony Fish (Osteichthyes): Bony fish have a skeleton made of bone, which is hard and calcified. Their bones are lightweight and provide support and protection to the body.

- Cartilaginous Jawless Fish (Agnatha): Cartilaginous jawless fish have a skeleton made of cartilage, which is a flexible, non-calcified connective tissue. Cartilage provides support and flexibility but is less rigid than bone.

2. Jaw Anatomy:

- Bony Fish: Bony fish have jaws that are composed of bone and are hinged to the skull. These jaws allow bony fish to open and close their mouths for feeding and respiration.

- Cartilaginous Jawless Fish: Cartilaginous jawless fish, as their name suggests, lack jaws. Instead, they have a round, suctorial mouth that they use for feeding. They do not have hinged jaws like bony fish.

3. Gill Structure:

- Bony Fish: Bony fish have a series of bony gill arches, each supporting a double row of gill filaments. These structures allow bony fish to extract oxygen from water.

- Cartilaginous Jawless Fish: Cartilaginous jawless fish have a different gill structure. They have a series of cartilaginous gill arches, each with a single row of gill filaments.

4. Scales:

- Bony Fish: Bony fish have scales covering their body. These scales can be of different types, including cycloid, ctenoid, and ganoid scales.

- Cartilaginous Jawless Fish: Cartilaginous jawless fish usually lack scales or have rudimentary dermal denticles covering their skin.

5. Fins:

- Bony Fish: Bony fish typically have a variety of fins, including paired pectoral and pelvic fins, and unpaired dorsal, anal, and caudal fins.

- Cartilaginous Jawless Fish: Cartilaginous jawless fish have paired pectoral fins and a single unpaired caudal fin. They lack pelvic fins and dorsal and anal fins.

6. Examples:

- Bony Fish: Some well-known examples of bony fish include tuna, salmon, trout, bass, and goldfish.

- Cartilaginous Jawless Fish: Examples of cartilaginous jawless fish include hagfish and lampreys.

These differences in skeletal structure, jaw anatomy, and overall morphology reflect the diverse evolutionary paths taken by bony fish and cartilaginous jawless fish. Bony fish represent the vast majority of fish species, while cartilaginous jawless fish are a more primitive group that has survived since ancient times.