supracardinal vein

noun

su·​pra·​car·​di·​nal vein ˌsü-prə-ˈkärd-nəl-, -ˌprä-, -ˈkard-ᵊn-əl 

: either of two veins in the mammalian embryo and various adult lower vertebrate forms located in the thoracic and abdominal regions dorsolateral to and on either side of the descending aorta and giving rise to the azygous and hemiazygous veins and a part of the inferior vena cava