A clade is a fancy word for any group in a phylogenetic tree that includes an ancestor and all of its descendants. A simplified dinosaur tree is below.
Imagine that you have a pair of scissors and can cut the tree. You can tell a group is a clade because it would only take one “snip” to make the group “fall off” the tree. Five different clades have been marked on the tree with brackets. The clade marked 1 is clade Aves—the birds. The clade marked 2 is clade Theropoda—the theropods. Clades 2 and 3 are the two major groups of dinosaurs—clade Saurischia and clade Ornithischia. Finally, clade 5 is clade Dinosauria—the dinosaurs.
Triceratops belongs to two of the marked clades on this tree: 4 and 5. This means that Triceratops is both an ornithischian (clade 4) and a dinosaur (clade 5). Which clades do birds belong to? (Select all correct answers)
1
2
3
4
5
