Parts of a Cladogram – Root, Node, Clade and Outgroup

All 13 boxes on the diagram

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Parts of a tree 8

Root The base of the tree, the ancestor of every tip.
Branch A line of the tree. It stands for one lineage through time.
Node A point where one lineage splits in two. It stands for the common ancestor of the tips beyond it.
Tip The end of a branch, where a group is named. The groups at the tips are also called taxa.
Clade An ancestor and all of its descendants. Here: C, D, E and the node they share.
Sister groups Two groups that split from the same node. They are each other's closest relatives.
Outgroup A group from outside the one being studied. It leaves the tree at the base.
Derived trait A new trait that arose on this branch. Every tip beyond the mark inherited it: B, C, D and E.

Land vertebrates 5

Amphibians They have four limbs but no amniotic egg. Frogs, toads, salamanders and caecilians.
Mammals The only group on this tree with hair.
Lizards and snakes On this tree, the sister group of birds and crocodilians together.
Crocodilians Crocodiles, alligators and their kin: the closest living relatives of birds.
Birds The sister group of the crocodilians. Together they are the living archosaurs.

How this list was compiled: Every name checked on 2026-10-01 in two sources. The parts of a tree: (1) University of California Museum of Paleontology, Understanding Evolution, https://evolution.berkeley.edu/ (Understanding phylogenies: the root represents the ancestral lineage and the tips the descendants; a clade is a common ancestor and all its descendants. How to read trees: branches correspond to ancestor and descendant relationships within a lineage; the branching points, or nodes, represent the splitting of a lineage, and the node where two paths meet is the common ancestor; the tips are called taxa. Reading trees, a quick review: two descendants that split from the same node are sister groups; an outgroup is a taxon outside the group of interest and stems from the base of the tree. Building the tree: a derived character is one that evolved in the lineage leading up to a clade; four limbs is a shared derived character of the tetrapods) and (2) Wikipedia, Cladogram, Phylogenetic tree, Clade, Sister group, Outgroup (cladistics), Apomorphy and synapomorphy (root, node, leaves or tips, branch; a clade is a common ancestor and all of its descendants; a sister group is the closest relative of a given group; an outgroup is a more distantly related group used as a reference; an apomorphy or derived trait is a novel character that evolved from its ancestral form). The land vertebrates: (1) again, whose example tree sets the amphibians inside the four limbs group and outside the amniotic egg group, joins the mammals by hair, and joins crocodiles to dinosaurs and birds; (3) Wikipedia, Tetrapod (four limbs are the defining trait), Amniote (the amnion; mammals on one branch, reptiles and birds on the other), Mammal (hair or fur), Bird (the closest living relatives are the crocodilians, with which they form the archosaurs), Sauropsida; (4) Tree of Life Web Project, Amniota and Diapsida, http://tolweb.org/Amniota/14990 and http://tolweb.org/Diapsida/14866 (living diapsids are either lepidosaurs, the lizards and the tuatara, or archosaurs, the birds and crocodiles; the position of turtles is uncertain). Licence: own work

The drawing: Drawn for this site on 2026-10-01 from plain geometry. Own original chart; nothing traced or copied. Licence: own work

How it works

The parts of a cladogram are its root, nodes, branches and tips, and the groups it shows: a clade, sister groups and an outgroup. Name each lit box, then place five groups of land vertebrates on their tree.

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Read the tree from the root

The root is on the left and time runs toward the tips on the right. Every node is a split: one lineage becomes two. To see how closely two tips are related, trace both back to the node where their paths meet. The nearer that node is to the tips, the closer the relatives. The order of the tips down the page means nothing by itself.

Place the land vertebrates

A tick on a branch marks a derived trait, and every tip beyond it has that trait. On the second tree the amphibians sit beyond four limbs but before the amniotic egg, and the mammals carry the tick for hair. Snakes count as four-limbed here: they descend from ancestors with limbs.

Questions and answers

What are the parts of a cladogram?

The root at the base, branches, the nodes where branches split, and the tips, where the groups are named. A cladogram also shows clades, sister groups and often an outgroup, and it may mark derived traits with ticks across the branches.

What is the difference between a node and a clade?

A node is one point: the split where a common ancestor became two lineages. A clade is a whole piece of the tree: that ancestor and all of its descendants. Cut one branch off a tree and everything on it is a clade.

How do you label the cladogram of terrestrial vertebrates?

Start at the root. Amphibians branch off first, after four limbs arose. Then the amniotic egg sets apart the rest: mammals on one branch, and lizards and snakes, crocodilians and birds on the other, with birds and crocodilians as sister groups.

Where do turtles go on the tree?

Among the reptiles, but the exact branch is disputed. Some studies set turtles beside the birds and crocodilians, and other sources call their position uncertain. This tree leaves them off for that reason.

Is a cladogram the same as a phylogenetic tree?

For most classroom purposes, yes: both are branching diagrams of how groups are related. Some biologists use cladogram for a tree whose branch lengths mean nothing, and phylogenetic tree where the lengths show time or the amount of change.