By clicking on the following links in order you can trace the history of life, essentially the cladogram, from the chordates to the dinosaurs. The Skull 1. Examine a series of skulls belonging to different groups of the Tetrapoda. Identify the frontals, nasals and maxillae on each specimen, and label on your drawings. Postcranial Skeleton 1.
Relationships Examine the cladograms below.
The following is a list of shared derived characters for Dinosauria, Ornithischia, and Saurischia. Keep in mind that the ornithischians and saurischians are equivalently-ranked sister taxa within the dinosaurs. For each skull, label the synapomorphies that you can see. Compare the skeletons of Allosaurus and the pigeon. Sketch the following features, labeling the bones, and describe the morphological changes needed to get from the primitive saurischian to avian condition.