We find that HoxC5 and HoxB8 have anterior expression boundaries at the level of the 6th pre-vertebra, HoxA6 at the 5th pre-vertebra (the first rib-bearing vertebra), HoxC6 at the 7th pre-vertebra and HoxB6 at the 3rd pre-vertebra (Figs. 4A–E).
Comparison with the expression data obtained for the snake (as in Table 1) shows that a relatively normal cervico-dorsal transition, although slightly elongated, is patterned in snakes (schematically depicted in Fig. 4F).
Interestingly, the expression of HoxA6 corresponds to the transition from rib-bearing to rib-less vertebrae at pre-vertebra level 4 in the snake and pre-vertebra 5 in the anole lizard.
However, all the other skeletal anatomical features associated with this transition are absent in snakes.