Fig 1. Character states and scores describing the degree of sutural closure and interdigitation in some American alligator skulls.

A, The blue arrows show an open and a partially closed suture on MOR OST 155. B, The blue arrow shows a closed suture (with its suture line still visible) on MOR OST 1029. C, The blue arrows show two obliterated sutures (with their suture lines morphologically invisible) on MOR OST 1029. D, The colored lines show the different degrees of interdigitation: a straight (yellow line), slightly interdigitated (orange line) and a very interdigitated suture (red line) on MOR OST 155. These interdigitation degrees are based on those in Herring [82].