The number of vertebrae in the different species of catadromous freshwater eels may be a key morphological factor not only for species identification, but also as a reflection of their species-specific scale of migration. The number of vertebrae of the 15 species and 3 subspecies (N = 11,699) of anguillid eels ranges from 100 to 119. Temperate eels (5 species and 1 subspecies) distributed in higher latitudes have a higher number of vertebrae than the tropical eels (10 species and 2 subspecies) in lower latitudes. A strong, positive correlation was found between the mean size of glass eels at recruitment into freshwater habitat and the mean numbers of vertebrae (pleomerism), and between the larval migration duration of leptocephali and the mean number of vertebrae. Furthermore, vertebrae counts showed a correlation with distance or larval migration duration from the spawning area to freshwater habitats, suggesting selection for vertebral number during larval and adult oceanic migration when anguillid species diversified from tropical eels to temperate eels. These findings suggest that the vertebral number in species of Anguilla may reflect the migratory characteristics of the species through their swimming performance and survival in the ocean during their long evolutionary history.