Brain Behav. Evol. 47(4): 214-218. 3 figs.

–Concludes from dissections of T. manatus cervical nerves that the presence of only six cervical vertebrae in manatees reflects a developmentally early reorganization of predetermined cervical mesoderm into fewer segments, rather than ontogenetic elimination of a vertebra without corresponding reduction of spinal root number. The relationship of the limb and its innervation to the cervical-thoracic boundary has not been altered.