Inset: a minimal representation of the Hedgehog family in vertebrates, to highlight the classically-described relationships between Sonic, Indian, and Desert groups (see text, Introduction). A and B are Neighbour-Joining (NJ) and Bayesian phylogenetic trees (aligned aminoacids) of 28 (NJ) and 27 (Bayes) Hedgehog family members including the presently found lamprey members (black arrowhead), with the fly and amphioxus Hhs used as out-group. Bootstrap values are given and the 3 orthology groups are indicated on the right (Sonic, Shh; Indian, Ihh; and Desert, Dhh). C is an amino-acid alignment of lamprey Hh proteins with gnathostome family members. The functional domains (HH signal and Hint domain) are indicated, as well as the exon (E) junction positions (e., g., E1/E2). The regions corresponding to Hha- and Hhb-specific in situ hybridization probes used in Figure 3 are also indicated, as well as the previously isolated Lf probe used in [23].