Gnathostomes

Definition

Gnathostomes are jawed vertebrates, encompassing a broad group including fishes and tetrapods. They evolved from jawless ancestors and are characterized by the presence of true jaws formed from gill arches.

5 Must Know Facts For Your Next Test

1. Gnathostomes include all modern vertebrates except for lampreys and hagfish.
2. The evolution of jaws allowed gnathostomes to exploit a wider range of food sources.
3. They possess paired fins or limbs, which enhance mobility and stability in water or on land.
4. Gnathostomes have a more complex skeletal structure compared to jawless vertebrates, with ossified bones.
5. Major groups within gnathostomes include Chondrichthyes (cartilaginous fishes) and Osteichthyes (bony fishes).

Review Questions

• What anatomical feature distinguishes gnathostomes from other vertebrates?
• How did the evolution of jaws benefit gnathostomes?
• What are the major groups that fall under gnathostomes?

Related terms

Chordates: Animals possessing a notochord, dorsal nerve cord, pharyngeal slits, endostyle, and post-anal tail at some point in their life cycle.

Fishes: Aquatic vertebrates that typically have gills, fins, and scales.

Tetrapods: Vertebrates with four limbs or limb-like appendages, including amphibians, reptiles, birds, and mammals.