Inferences of Diplodocoid (Sauropoda: Dinosauria) Feeding Behavior from Snout Shape and Microwear Analyses
Figure 4
Metrics used to determine snout shape in this study.
Snout depicted based on Diplodocus in Figure 3, anterior towards top of page. From left to right: the upper arcade index (uAI) measures snout breadth by taking the ratio of arcade width to arcade depth (higher numbers indicate squarer snouts); the premaxilla-maxilla index (PMI) is determined by taking the ratio of an area covered by the snout within a predetermined triangle to the area of that triangle (higher numbers indicate squarer snouts); the premaxillary divergence angle (PMDA) determines squareness by measuring the divergence of the anterior margin of the premaxilla from perfectly square (higher numbers indicate greater divergence from square and therefore roundness). The angle of the hypotenuse of the triangle used to calculate PMI (26°; 64° internal angle) is based on the angle used in the PMI's parent metric, the PSI [44].