part of part of immediate transformation of nervous system central nervous system (...) at some stage of its development, every chordate exhibits five uniquely derived characters or synapomorphies of the group: (...) (4) a single, tubular nerve cord that is located dorsal to the notochord (...) (reference 1); The neural tube is destined to differentiate into the brain and spinal cord (the central nervous system) (reference 2); Taken together, our data make a very strong case that the complex molecular mediolateral architecture of the developing trunk CNS (central nervous system), as shared between Platynereis and vertebrates, was already present in their last common ancestor, Urbilateria. The concept of bilaterian nervous system centralization implies that neuron types concentrate on one side of the trunk, as is the case in vertebrates and many invertebrates including Platynereis, where they segregate and become spatially organized (as opposed to a diffuse nerve net). Our data reveal that a large part of the spatial organization of the annelid and vertebrate CNS was already present in their last common ancestor, which implies that Urbilateria had already possessed a CNS (reference 3).[well established][VHOG] AAO:0000090 BAMS:CNS BILA:0000080 BTO:0000227 CALOHA:TS-0150 CNS EFO:0000908 EHDAA2:0000225 EHDAA:828 EMAPA:16470 EMAPA:16754 EV:0100163 FBbt:00005094 FMA:55675 GAID:570 MA:0000167 MAT:0000457 MESH:D002490 OpenCyc:Mx4rvzYt3pwpEbGdrcN5Y29ycA Part of the nervous system which includes the brain and spinal cord.[AAO] TAO:0000012 The brain and spinal cord. Kimmel et al, 1995.[TAO] The central nervous system (CNS) is the part of the nervous system which includes the brain, spinal cord, and nerve cell layer of the retina (CUMBO). The central nervous system is the core nervous system that serves an integrating and coordinating function. In vertebrates it consists of the neural tube derivatives: the brain and spinal cord. In invertebrates it includes central ganglia plus nerve cord. UBERON:0001017 UMLS:C0927232 VHOG:0000293 XAO:0000215 ZFA:0000012 cerebrospinal axis neuraxis systema nervosum centrale uberon ectoderm-derived structure organ system subdivision future central nervous system