Is the first hieroglyph really a crocodile skin?  Are you aware that the ancient Egyptians associated the color black with the night, as well as death & mystery.  And, conversely, night, death, and mystery with the color black.  The owl, therefore, became an apt symbol for all three.  The Nile crocodile also, since it could be a nocturnal predator, was associated with the night and death.  But for the life of me, no matter how hard I search, I can not come up with one specimen of crocodile scale containing a multiple-serrated edge.  However, when I compared Gardiner's sign I6 with the tip of an owl wing, I came up with the following: