The maximum likelihood tree inferred from the concatenated amino acid sequences (2,942 residues) of seven proteins. Reliability index  and the bootstrap probability for each branch are indicated before and after a slant, respectively. This tree corresponds to topology a in Tables 1 and 2. Topology b in Tables 1 and 2 is indicated by a dotted arrow. A dash-dotted line indicates the position of plownose chimaera inferred from six proteins. Branch lengths are proportional to accumulated amino acid substitutions.