Domeykosaurus was 25 feet long and 6.5 feet wide, with the long neck and tail typical of titanosaurs. It was uncharacteristically gracile, with more slender limbs than are usually associated with its type. Paleontologists speculate that the herbivore most likely ate such plants as the extant genus Araucaria, also known as the "Monkey Puzzle Tree", which is native to the area.