Question

Origin evolution and general characters of agnatha​

Answer 1

Answer:

Explanation:

As the most primitive members of the vertebrates, agnathans differ from all others in several important respects. First, they lack hinged upper and lower jaws and instead have unhinged circular mouths. They also lack the paired appendages (fins or limbs) that are found in other vertebrates. In addition, the internal skeleton of agnathans is not bony but cartilaginous . However, many extinct agnathans had extensively developed bony plates directly under the skin. These were most often found in the region of the skull and served as a protective armor. Bony plates are not present in extant agnathan species