ABSTRACT
Living members of the Chondrostei are the northern hemisphere anadromous and freshwater sturgeons (Fig. 8.1) and the paddlefish of freshwaters of N. America and China (Nelson 2006) (Fig. 8.7). Despite the fact that several synapomorphies are reductive, the Chondrostei appear to comprise a monophyletic group. Among living forms they are usually considered to be the sister-group of the Neopterygii (Lauder and Liem 1983; Nelson 2006) and this is supported by Orti and Li (Chapter 1) from an analysis of nuclear DNA sequences for 8 genes and 11,766 base pairs in 29 taxa. However, Li, Lu and Orti (2008), in an analysis of 10 nuclear genes and 7995 base pairs, find the Chondrostei (represented in their analysis only by Polyodon) to be the sister group of Polypterus. If so, placement of Polypterus in the Chondrostei would be permissible as in the spermatozoal phylogeny in Chapter 7 (Fig. 7.1). However, the evidence for a sister relationship of Cladistia and all other ray-finned fishes has strong support (see Chapters 1 and 7).
