Gnathostomes

Definition

Gnathostomes are a group of vertebrates that possess jaws. They include both cartilaginous and bony fish, as well as all tetrapods.

5 Must Know Facts For Your Next Test

1. Gnathostomes first appeared in the fossil record around 450 million years ago during the Silurian period.
2. The development of jaws allowed gnathostomes to exploit new feeding strategies, significantly diversifying their ecological niches.
3. Gnathostomes are divided into two major groups: Chondrichthyes (cartilaginous fish) and Osteichthyes (bony fish).
4. All land vertebrates, including amphibians, reptiles, birds, and mammals, are descendants of early gnathostomes.
5. The evolution of paired fins and later limbs in gnathostomes was crucial for the transition from aquatic to terrestrial life.

Review Questions

• What key feature distinguishes gnathostomes from other vertebrates?
• During which geological period did gnathostomes first appear?
• Name the two major groups into which modern gnathostomes are divided.

Related terms

Chondrichthyes: A class of gnathostomes that includes sharks, rays, and skates, characterized by having a skeleton made of cartilage.

Osteichthyes: A diverse class of gnathostomes known as bony fish, which have a skeleton primarily composed of bone.

Tetrapods: A superclass of gnathostomes that includes all four-limbed vertebrates such as amphibians, reptiles, birds, and mammals.