Lampreys are ancient.
450 million years ago ancient, fossils of them having been discovered from the late Silurian and Devonian periods. On Saturday, whilst paddling in the river with the local archaeology group I quite unexpectedly came across some in the shallows.
They belong to a small group of stone suckers called Agnatha (meaning jawless) that are the most primitive of all living vertebrates. Eel-like in appearance, the seven gill pores behind each eye are useful identifiers, along with the distinct, sucker like mouth with strong, horny, rasping teeth.
Further information on these fascinating creatures and their life-cycle can be found in this excellent PDF from English Nature.