The vertebrate body axis is divided into a number of segments or 'somites', such as the number of vertebrae. But what controls vertebra number, and its variation between species? This paper postulates that the number depends on a balance between the division of the body into somites (the segmentation clock rate) and the overall rate of development, as established by showing that the large number of vertebrae in snakes comes from a much greater segmentation clock speed in snakes, relative to development as a whole, than in other vertebrates.
- Céline Gomez
- Ertuğrul M. Özbudak
- Olivier Pourquié
