The thick tail mutation contains anomalies of the axial skeleton.

Analysis of the skeletal effects of thick tail (Tht), a radiation-induced mutation, has revealed numerous anomalies in the axial skeleton. The affected regions include the atlantal-occipital region as well as the lumbar (Lu) and caudal (Ca) vertebrae in which the ossified adult structures are either missing or reduced in size. Skeletons of juvenile Tht heterozygotes exhibit a malformed occipital bone, atlas, smaller Ca vertebrae, and delayed ossification of the affected adult structures. The diminished amount of cartilage and bone suggests that the Tht gene may be functioning during the formation of these tissues.