Dorsal fin of Cyclostomata
It a have slender eel-like body measuring from 45 cm to 1 m in length. It process two dorsal fins the first one is the anterior dorsal fin, which is the smallest and the second one is the posterior dorsal fin which is the largest and extending towards the caudal fin, mid-dorsal region of the body.
About the Animal
Cyclostomes’ are jawless vertebrates, They are primitive vertebrates. The cyclostomes are marine or fresh-water vertebrates. It includes the lampreys and hag fishes. They have cartilaginous skulls and tooth-like structures composed of keratin. Hagfish have no true fins and have six or eight barbels around the mouth and a single nostril. Their eyespots when present can detect light, but as far as is known none can resolve detailed images, some hagfish species are thought to be hermaphroditic, having both an ovary and a testicle. They lack true jaws and paired fines. The nostril is single and median. And they possess a two chambered heart.