datation

Rates of skeletal character evolution in the skull and postcranial skeleton of hadrosauroids. Cladograms illustrate the results from branch likelihood tests for two morphological partitions: skull (cranium and mandible) (A) and postcranial skeleton (B). In both cladograms, results from the branch likelihood tests are summarized on a strict consensus tree derived from four separately analyzed MPTs, each with 100 dating replicates (a total of 400 Hedman-dated phylogenies). Pie charts on branches illustrate the proportion of dating replicates that showed significantly high rates (red), slow rates (blue), or nonsignificant average rates (white). No pie charts are plotted on branches that showed nonsignificant rates in 100% of dating replicates. Branches that showed high rates (red) in more than 50% of dating replicates are doubled in length. See the Supplementary Material for Hedman-based results plotted separately for each MPT (Supplementary Fig. S2) and for results using the MBL dating method (Supplementary Fig. S3). Silhouettes were created by Scott Hartman and were downloaded from http://phylopic.org (Creative Commons license CC BY 3.0).

Natural-colour satellite image of part of the Kaiparowits Basin (a central portion of Grand Staircase-Escalante). The branch-like shapes are networks of canyons carved by rivers that dried up millions of years ago. The ridge running roughly north-south through the scene is the Cockscomb, which is surrounded by distinct rock formations deposited at different times in the geologic past. West of the Cockscomb is the Navajo Sandstone, dating from the Triassic. East of the Cockscomb are two formations from the Cretaceous: the light-toned Wahweap and darker Kaiparowits.