Gnathostomata

Gnathostomata is a group of vertebrates that includes all animals with jaws. The group is one of the largest and most diverse in the animal kingdom, including all birds, mammals, reptiles, amphibians, and most fish. The name "Gnathostomata" comes from the Greek words for "jaw" (gnathos) and "mouth" (stoma).

Characteristics

Gnathostomata are characterized by the presence of jaws, which are used for capturing and processing food. This is a significant evolutionary development, as it allows these animals to consume a wider range of food sources than their jawless counterparts. Other defining characteristics of Gnathostomata include paired appendages (fins, wings, or limbs), a three-part brain, and an internal skeleton made of bone or cartilage.

Evolution

The first gnathostomes appeared in the Silurian period, around 440 million years ago. These early jawed vertebrates were likely marine creatures, as the oldest gnathostome fossils are found in marine sediments. Over time, gnathostomes diversified and adapted to a wide range of environments, from the deepest oceans to the highest mountains.

Classification

Gnathostomata is divided into two major groups: the Chondrichthyes, which includes sharks, rays, and chimaeras; and the Osteichthyes, which includes all bony fish and tetrapods (four-limbed vertebrates). The latter group is further divided into the Actinopterygii (ray-finned fish) and Sarcopterygii (lobe-finned fish and tetrapods).

See also

• Chondrichthyes
• Osteichthyes
• Actinopterygii
• Sarcopterygii
• Evolution of fish
• Vertebrate

References

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