EVOLUTION AND DIVERSIFICATION OF ANTARCTIC NOTOTHENIOID FISHES

Antarctica supported fossil ichthyofaunas during the Devonian, Jurassic, Cretaceous and Eocene/Oligocene. These faunas are not ancestral to each other, nor are they related to any component of the modern fauna. About one hundred species of notothenioids dominate a modern fauna of over 200 species of bottom fishes. This highly endemic perciform suborder is not represented in the fossil record of Antarctica. Notothenioids may have evolved in situ on the margins of the Antarctic contient while gradually adapting to cooling conditions during the Tertiary. Cladistic studies indicate that notothenioids are a monophyletic group, but a sister group has not been identified among perciform fishes. With relatively few non-notothenioid fishes in Antarctic waters, notothenioids fill ecological roles normally occupied by taxonomically diverse fishes in temperate waters. There are six notothenioid families: Bovichtidae, Nototheniidae, Harpagiferidae, Artedidraconidae, Bathydraconidae and Channichthyidae. Aspects of their biology are briefly considered with emphasis on the Nototheniidae, the most speciose family. Evolutionary diversification within this family allows recognition of species which are pelagic, cryopelagic, benthopelagic and benthic.