Fig. 3

Hox code and vertebral morphology through deep time. a Effect of single loss-of-function mutations in Hox4 and Hox5 paralog group on the cervical vertebral column in the mouse. b Overview and schematic illustration of characteristic features in the cervical vertebral column during synapsid evolution. The correlation between somitic Hox gene expression pattern and morphological modularity in the neck of Mus musculus (top right) allows to hypothesize about the Hox code in fossil relatives on basis of major morphological changes. Major morphological and reconstructed genetic changes are indicated in blue. The mouse Hox code is based on references provided in Table 3. c The correlation between somitic Hox gene expression pattern and morphological modularity in the neck of the crocodile serves as outgroup configuration (based on [13]). The crocodilian Hox code is based on references [8, 9, 13]