Κλάδος: Διαφορά μεταξύ των αναθεωρήσεων

| page = 217 }}</ref> The ancestor can be an organism, [[population]], or [[species]].<ref>The [[PhyloCode]], [http://www.ohio.edu/phylocode/art1-3.html#chapter1 Chapter 1]</ref> The common ancestor of any group of reasonable size and most of that ancestor's descendants have typically been long extinct.<ref group=note>This may not be true in very small and recent clades, where the common ancestor and all descendants are still living.</ref> It is not necessary for a clade to contain any living representatives. In most cases, the actual ancestor is a hypothetical rather than an actual species, as the likelihood finding a [[fossil]] of the ancestral species is slim. Should an actual ancestor be found, the computer program used in cladistic analysis will not be able to recognise it as such, and display it as the sister group to its descendant clade.<ref group=note>The current cladistic computer program [[PAUP]] do not take time into account, and will present all species/specimen as contemporary.</ref>