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They are parasitic, in their adult stage, usually feeding on fish.

They are parasitic, in their adult stage, usually feeding on fish. They are morphologically similar to eels. They are considered to be the only living vertebrate without true jaws and are thus called Agnatha. Cyclostomata is made of hagfish and lampreys.

The Cyclostomata are the living agnathans (Gr., cyklos = circular + stoma = mouth), they are primitive in many respects but specialized in others. The suctorial mouth is round and ventral (thus, Cyclostomata). The buccal cavity has a robust tongue with epidermal teeth from which they rasp fish flesh. They are the only living, jawless vertebrates. They have 6-14 pairs of inner gills of different species. Gill-chambers are round bags (so, Marsipobranchii). The skin is soft and devoid of scales, paired appendages are absent, though cartilaginous fin rays support the median fins.

Possibly the resemblance of those two classes is the product of convergent evolution. They do, however, show significant and basic morphological differences that can be attributed to their long phylogenetic separation and different habitats and habits.

Members of this order are called lamps or lamp eels, or lamps, or pride in the sand, etc.

Examples: The torches. Thirty species over. Petromyzon, Ichthyomyzon, Lampetra.

Order representatives are termed hagfishes. They are marine only.

Examples: Hagfishes. About 15 species Myxine, Eptatretus (= Bdellostoma), Paramyxine.

Besides these, the ammocoete larva of lampreys resembles Amphioxus as follows:

Around 50 cyclostome species are recognized. We belong to two main groups (Myxiniformes and Petromyzontiformes). They are termed subclasses, orders, or families in different ways. They are combined in the class Cyclostomata because they possess a round jawless mouth.

They are parasitic, in their adult stage, usually feeding on fish. They are morphologically similar to eels. They are considered to be the only living vertebrate without true jaws and are thus called Agnatha. Cyclostomata is made of hagfish and lampreys.

The Cyclostomata are the living agnathans (Gr., cyclos = circular + stoma = mouth), they are primitive in many respects but specialized in others. They are a modified and degenerate offshoot of the primitive stalk in the Devonian vertebrate, which arose. They are parasites or scavengers on fishes in the adult state. They have round bodies with compressed lateral or diphycercal legs. They superficially mimic eels.

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