in taxon capable of capable of lymph circulation Mammalia Sarcopterygii Anura Crocodylidae Serpentes lymph heart Lymph hearts consist of three tissue layers, a tunica interna intima consisting of an endothelial cell lining, a middle tunica media that contains the musculature of the lymph heart, and an outer tunica externa made up of fibroelastic tissue [DOI:10.1152/japplphysiol.00201.2013] Wikipedia:Lymph_heart UBERON:0015202 A circulatory organ that is reponsible for pumping lymph throughout the body. Caecilians posses a lymph heart at every segment boundary thus having up to 200 in number. accessory circulatory organ