We broadly identified two morphologically distinct types of embryonic malformations. On the one hand, malformations typically observed in Alx3-deficient mutants32, affecting the craniofacial mesenchyme and the forehead, or defects of the cranial neural tube at the prosencephalic and/or mesencephalic levels. These are referred to in the present study as craniofacial malformations. On the other hand, malformations consisting mostly of tail flexion defects similar to those defined by Copp et al. 44, occasionally including dorsal neural tube closure defects at the rhombencephalic or spinal levels. These are referred to in this study as caudal malformations.