What is the Difference Between Agnathans and Gnathostomata?

The main difference between Agnathans and Gnathostomata lies in the presence or absence of jaws. Agnathans, also known as Cyclostomata, are a group of fish that lack jaws, while Gnathostomata possess true jaws. Here are some key differences between the two groups:

Agnathans (Cyclostomata):

• Mouth is circular and without jaws
• Paired appendages (fins and limbs) are not present
• Notochord is present throughout life
• There are 8 or 10 pairs of cranial nerves
• Only a single median nostril is present
• No organized pancreas and spleen
• They are cold-blooded

Gnathostomata:

• Mouth has jaws
• Paired appendages (fins and limbs) may be present
• Notochord is present in the embryonic stage and is replaced by a vertebral column in adults
• There are 10 or 12 pairs of cranial nerves
• Paired nostrils are present
• Pancreas and spleen are present as distinct organs
• They may be cold-blooded or warm-blooded animals

Gnathostomata is further divided into two superclasses: Pisces (fishes) and Tetrapoda (animals with limbs).

Comparative Table: Agnathans vs Gnathostomata

The main difference between Agnathans and Gnathostomata lies in the presence or absence of jaws. Here is a table summarizing the differences between the two groups:

Agnathans, such as hagfishes and lampreys, possess a circular mouth without jaws, while Gnathostomata, which include sharks, rays, and bony fishes, have a mouth with jaws. Additionally, Agnathans lack paired appendages, while Gnathostomata possess them in the form of fins and limbs. The notochord is present throughout life in Agnathans, but it is present only in the embryonic stage in Gnathostomata, being replaced by a vertebral column in adults.