Figure 1.

An unrooted ML tree including gnathostomes and the sea lamprey. The tree was reconstructed from analyses of the concatenated amino acid sequences of 12 mitochondrial protein-coding genes as described in the text. For scientific names, see Materials and Methods. The sea lamprey was replaced by the hagfish, the lancelet, or three echinoderms in three parallel analyses. Like the lamprey, all of these taxa received a position between the lungfish and the amniotes.