A phylogenetic tree that specifies ancestral and descendant species, thus indicating the direction of the evolutionary path.

A directed tree with designated root node. See Also Tree.

tree in which one vertex has been distinguished. The distinguished vertex is called the root of the tree.

a tree in which one of the vertices is the root of the tree

a tree where one node is designated as root

a tree with a distinguished vertex, called the root of the tree

A cladogram with a hypothetical ancestor, which equates to the root, which is the node at the base of the tree. When outgroups are used, this is the node that connects the outgroups to the ingroup, and which thus specifies the direction of evolutionary change among the character-states (cf. unrooted tree).