Agnatha, meaning "jawless," is an ancient group of fish that includes modern lampreys and hagfish. These creatures are known for their lack of jaws, which distinguishes them from other fish. Instead of jaws, they have circular mouths with rows of getained teeth-like structures. Agnatha has a long evolutionary history, dating back to theCambrian period, and is considered one of the earliest forms of vertebrate life.
Cartilaginous Skeletons
Agnatha have skeletons made entirely of cartilage rather than bone, which makes them more flexible and lighter than their bony counterparts. This cartilaginous structure is similar to that found in sharks and rays, but unlike those groups, agnathans do not have true vertebrae, although they possess a notochord that gives some structural support. The cartilaginous skeleton is one of the shared traits that link agnathans to more advanced vertebrates, highlighting their role in the evolutionary history of fish.
Ancient Lineage
Agnatha is considered to have one of the oldest lineages in vertebrate evolution, with ancestors dating back to the Cambrian period over 500 million years ago. Their primitive characteristics, such as the absence of jaws and the presence of a notochord, suggest that they are closely related to the early origins of vertebrates. The study of agnathans helps scientists understand the evolutionary transitions from invertebrates to vertebrates, making them crucial for piecing together the history of animal life in the ocean.