The phylogeny of the Craniata, with particular reference to the significance of fossil “agnathans”

Abstract

ABSTRACT The phylogenetic relationships of the extant Craniata are analyzed, and the position of the best known fossil groups of jawless craniates is discussed. Some of the patterns obtained are inconsistent with previous opinions on the phylogeny of the Craniata, e.g. on the question of monophyly of the Cephalaspidomorphi. It is concluded that the fossil jawless Craniata provide little information on the affinities of the Craniata, but they do provide complementary data on distribution of characters. According to their respective positions in the cladogram, these fossil groups allow determination of polarity of some characteristics, such as paired fins, naso-hypophysial complex, and eye musculature.