It is caused by non-closure of the foramen ovale, connecting the right with the left side of the heart, and the consequent mixing of the venous with the arterial blood.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
At the posteroventral corner of the naris a foramen opens onto the lateral surface of the maxilla.
"Two New Pelycosaurs from the Lower Permian of Oklahoma"
Richard C. Fox
Probably not; and more especially if it is a lumbar artery, and injured in the foramen through which it passes from the vertebra.
"Report on Surgery to the Santa Clara County Medical Society"
Joseph Bradford Cox