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Evolution

Tracing the evolution of these species has been problematic given the paucity of good fossils. DNA sequencing has become the preferred approach to understanding speciation.

The group containing chimaeras and their close relatives (Holocephali) is thought to have diverged from Elasmobranchii (the group containing modern sharks and rays) during the Devonian, over 380 million years ago. The oldest known chimaeriform is Protochimaera from the Early Carboniferous (338-332 million years ago) of Russia, which is more closely related to modern chimeras (Chimaeroidei) than any other known extinct groups of Chimaeriformes. The earliest known remains attributable to modern chimaeras are known from the Early Jurassic (Pliensbachian) of Europe, but egg cases from the Late Triassic of Yakutia, Russia and New Zealand that resemble those of rhinochimaerids and callorhinchids respectively indicates that they had a global distribution prior to the end of the Triassic. Unlike modern chimaeras, Mesozoic representatives are often found in shallow water settings.

Extinct chimaeriforms include: