Its position is not indicative of a narial opening, either. Basilemys has a deep premaxillary border that is just below the external narial opening. The folds enclose air passages extending the narial passages to the front of the snout. The anterior portion is sub-circular and is thought to be the true narial opening. Ankylosaurids also have an S-shaped narial passage. The rostrum possessed narial openings wider than that of modern Anseriformes. The nostrils are oval in shape and they possess narial lappets on the outer margin. Resembling Adocus and Zangerlia, the external narial opening of Basilemys is small. The narial fenestra of "Teraterpeton" is approximately 1.5 times longer than the eye socket.