For snakes species the vertebral number and body size are linked, since early in their life the bones and muscles of the snake will get longer for the animal get bigger, being in continuously length grow. The vertebral number can still be the same in the organisms, however as it gets older the bone structure will go wide and consequently the body will be elongated. Therefore, there is a direct correlation between the vertebral width and the body length in snake species.
The scientists were able to determine that because of the study of fossils, the fossils are used to estimates the phenotypes traits of especies by the analysis of bone structures and the correlation of those to the animals of today, drawing anatomical parallels for groups of organisms and their functions and habitats.