Petromyzontiformes (Lampreys)

Lampreys (sometimes also called, inaccurately, lamprey eels) are any jawless fish of the order Petromyzontiformes, placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like sucking mouth. The common name "lamprey" is probably derived from Latin lampetra, which may mean "stone licker" (lambere "to lick" + petra "stone"), though the etymology is uncertain.
There are about 38 known extant species of lampreys. Parasitic species are the best known, and feed by boring into the flesh of other fish to suck their blood; but only 18 species of lampreys are parasitic. Parasitic lampreys also attach themselves to larger animals to get a free ride. Adults of the non-parasitic species do not feed; they live off reserves acquired as ammocoetes (larvae), which they obtain through filter feeding.
The lampreys are a very ancient lineage of vertebrates, though their exact relationship to hagfishes and jawed vertebrates is still a matter of dispute.
Check out Wikipedia for more details!
== Families ==
* Petromyzontidae