Externally
skin
without jaws
Agnatha, also known as jawless fish, lack jaws and scales. They have a cartilaginous skeleton, a round mouth, and a single nostril on their head. Agnatha are also known for their ability to produce slime as a defense mechanism.
Class Agnatha
with gills; they're fish!
I don't know but i will do some research...
jawless fish. not very common today, but they were in the past.
no they have large bonelikes structures called the stonnes.
Agnatha, such as lampreys and hagfish, have a two-chambered heart. The heart consists of an atrium and a ventricle, which pump blood through the circulatory system.
Agnatha, which includes jawless fish like lampreys and hagfish, have all three germ layers: ectoderm, mesoderm, and endoderm. They exhibit the typical triploblastic organization found in most animals.
Examples of agnatha, or jawless fish, include lampreys and hagfish. These fish are characterized by their lack of jaws, paired fins, and scales. They are considered primitive vertebrates and play important roles in marine ecosystems.