part_of part of part of develops from develops from ends during starts during spinal cord notoplate floor plate spinal cord floor Organizing center consisting of a small group of cells located at the ventral midline of the neural tube that influences the development of the nervous system, governing the specification of neuronal cell types and directing axonal trajectories. xenopus_anatomy floorplate XAO:0000306 multi-tissue structure NF stage 22 NF stage 66