develops from develops from immediate transformation of leptomeninx pia-arachnoid neuronames:2347 arachnoidea mater et pia mater BTO:0001634 UMLS:C0228126 arachnoid mater and pia mater SCTID:362303006 CALOHA:TS-0546 pia-arachnoid of neuraxis Wikipedia:Leptomeninges Pia mater or arachnoid mater. NLXANAT:090207 UBERON:0000391 NCIT:C32979 leptomeninges in FMA/NIF this is a superclass of PM/AM - in BTO it is the mereological sum. We go with superclass here, as we are naming the class in the singular FMA:231515 check relationship to secondary meninx meninx endomeninx Christopher J. Mungall