Fossil Record
Lamprey fossils are rare because cartilage does not fossilize as readily as bone. The first fossil lampreys were originally found in Early Carboniferous limestones, marine sediments laid down more than 300 million years ago in North America: Mayomyzon pieckoensis and Hardistiella montanensis, from the Mississippian Mazon Creek lagerstätte and the Bear Gulch Limestone sequence.
In the 22 June 2006 issue of Nature, Mee-mann Chang and colleagues reported on a fossil lamprey from the same Early Cretaceous lagerstätten that have yielded feathered dinosaurs, in the Yixian Formation of Inner Mongolia, laid down around some 120 million years ago. The new species, morphologically similar to Carboniferous and modern forms, was given the name Mesomyzon mengae ("Meng Qingwen's Mesozoic lamprey"). The exceedingly well-preserved fossil showed a well-developed sucking oral disk, a relatively long branchial apparatus showing branchial basket, seven gill pouches, gill arches and even the impressions of gill filaments, and about 80 myomeres of its musculature. Unlike the North American fossils, its habitat was almost certainly freshwater.
Months later, in the 27 October issue of Nature, a fossil lamprey even older than the Mazon Creek genera, dated 360 million years ago, was reported from Witteberg Group rocks near Grahamstown, in the Eastern Cape of South Africa. This species, dubbed Priscomyzon riniensis still strongly resembled modern lampreys despite its Devonian age.
Read more about this topic: Lamprey, Taxonomy and Systematics
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