part of part of in taxon Petromyzontiformes hematopoietic system immune system hemopoietic organ immune organ supraneural body The supraneural body from hematopoietically stimulated lampreys appears to be histologically-similar to 'bone marrow' in higher vertebrates and contains all blood cell lineages and their precursors, including lymphocytes at all stages of maturity One of the primary immunological organs of the adult lamprey is the supraneural body. This structure lies dorsal to spinal column and becomes heavily populated with lymphocytes following after immune challenge. dorsal fat body pro-vertebral arch UBERON:0009102