The diagram is called A. A cladogram
What is a Cladograms ?
Diagrams known as "cladograms" show the links between various taxonomic groups, or "clades." Cladograms reconstruct the taxa's evolutionary history, or phylogeny, by showing these links. Phylogenies and trees are other terms for cladograms.
A cladogram is a branching tree-like graphic that shows the links between organisms in terms of evolution (phylogenetics). There are two branching lines of descendance at each node, or point of divergence, signifying evolutionary separation from a common ancestor.