part of part of composed primarily of immediate transformation of membrane organ meninx BTO:0000144 CALOHA:TS-1177 EFO:0000867 EMAPA:32660 EV:0100312 FMA:9589 GAID:687 In fishes, the meninges consist of a single membrane, the primitive meninx, wrapped around the brain and spinal cord. With the adoption of terrestrial life, the meninges doubled. In amphibians, reptiles, and birds, the meninges include a thick outer dura mater derived from mesoderm and a thin inner secondary meninx. (...) In mammals, the dura mater persists, but division of the secondary meninx yields both the arachnoid and the pia mater from ectomesoderm.[well established][VHOG] MA:0001113 MAT:0000113 MESH:D008578 Membrane covering the brain and spinal cord. It is represented by a single layer in fishes, two in amphibians, reptiles and birds and three in mammals (named dura mater, arachnoid and pia mater). [TFD][VHOG] Membrane organ that surrounds the brain and the spinal cord. Not consider part of the CNS/neuraxis in FMA OpenCyc:Mx4rwDOl8JwpEbGdrcN5Y29ycA TAO:0001355 UBERON:0002360 UMLS:C0025285 VHOG:0001295 Whereas cyclostomes and fishes only have a single envelope called the primitive meninx, amphibians have two layers, consisting of an outer dura mater which is extremely dense and protective, and a pia-arachnoid or secondary meninx which is more delicate and vascular. Mammals have three meninges: pia mater (which follows all the convolutions of the brain and is the most interior), the arachnoid layer (which is delicate and sends strands to the pia mater), and the dura mater (the outer, more protective meninx). ZFA:0001355 layer of meninges meningeal meningeal layer meninx primitiva uberon connective tissue ectoderm-derived structure future meninx structure with developmental contribution from neural crest meningeal cluster