ABSTRACT
The classification of the Sarcopterygii (lobe-finned fishes and derived relatives) employed here is chiefly that of Cloutier and Ahlberg (1996) which was adopted by Nelson (2006). Despite some equivocal results, molecular studies appear to confirm the finding (e.g. Meyer and Wilson 1990; Meyer and Dolven 1992) that lungfishes are the sister-group of the Tetrapoda though these two groups are also the closest relatives of Latimeria (Yokobori et al. 1994; Zardoya and Meyer 1996,1997a; b). From analysis of sequences of 44 nuclear genes Takezaki et a l (2004) concluded that the coelacanth, lungfish, and tetrapod lineages diverged within such a short time interval that their relationships appear to be an irresolvable trichotomy. All of these studies endorse the sarcopterygian status of Latimeria demonstrated by Hillis et al. (1991). The sister relationship between the Sarcopterygii and Acinopterygii is endorsed by Orti and Li (Chapter 1, Fig. 1.3) in a consideration of phylogenetic analyses of morphology and molecular data depicting the Coelacanthimorpha as the sister group of the Ceratodontiformes +Tetrapoda. In a molecular analysis of 8 genes, including 11,766 base pairs (Fig. 1.4) they find the Sarcopterygii to be the sister of the Actinopterygii, though sarcopterygian fishes are not represented.
