Sentence:  In this regard, a thorough and explanatory embryology-based classification of bony malformations of the craniovertebral junction has been elaborated by Pang and Thompson [87 ], who indicate that malformations of the arch of the atlas emerge from disturbances of the lateral zone of the upper cervical sclerotome (posterior arch) and the <WSD>hypochordal</WSD> bow (anterior arch). 
Meaning of the word marked with <WSD> tags:  ventral to the spinal cord