Polytomy

Cladograms B and C contain polytomies, where more than one branch descends from a single node.

An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches.^[1]^[2] A tree that contains any multifurcations can be described as a multifurcating tree.

^ Hancock, John M.; Zvelebil, Marketa J., eds. (2004-07-15). Dictionary of Bioinformatics and Computational Biology. Hoboken, NJ, USA: John Wiley & Sons, Inc. doi:10.1002/0471650129. ISBN 978-0-471-65012-6.
^ Drummond, Alexei J.; Bouckaert, Remco R. (2015). Bayesian Evolutionary Analysis with BEAST. Cambridge: Cambridge University Press. doi:10.1017/cbo9781139095112. ISBN 978-1-139-09511-2.

[1] Hancock, John M.; Zvelebil, Marketa J., eds. (2004-07-15). Dictionary of Bioinformatics and Computational Biology. Hoboken, NJ, USA: John Wiley & Sons, Inc. doi:10.1002/0471650129. ISBN 978-0-471-65012-6.

[2] Drummond, Alexei J.; Bouckaert, Remco R. (2015). Bayesian Evolutionary Analysis with BEAST. Cambridge: Cambridge University Press. doi:10.1017/cbo9781139095112. ISBN 978-1-139-09511-2.

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