( ( This ( rod-like strucxture ) ) ( ( is ( ( ( ( ( the notochord ) , ) ( ( the progenitor ) ( of ( the backbone ) ) ) ) or ) ( vertebral column ) ) ) . ) )
(ROOT (S (NP (DT This) (JJ rod-like) (NN strucxture)) (VP (VBZ is) (NP (NP (DT the) (NN notochord)) (, ,) (NP (NP (DT the) (NN progenitor)) (PP (IN of) (NP (DT the) (NN backbone)))) (CC or) (NP (JJ vertebral) (NN column)))) (. .)))
This rod-like strucxture is the notochord, the progenitor of the backbone or vertebral column.
(ROOT (S (NP (NNP Backbone)) (VP (VBZ is) (NP (NP (DT another) (NN name)) (PP (IN for) (NP (DT the) (JJ vertebral) (NN column))))) (. .)))
Backbone is another name for the vertebral column.