A vein in the mammalian embryo or the adult of some lower vertebrates that is located on each side of the abdominal region ventromedial to the mesonephros and that in mammals participates in the formation of the inferior vena cava and the renal vein [ https://www.worldcat.org/search?q=bn%3A0073040584 http://www.merriam-webster.com/medical/subcardinal%20vein ]