On Mon, 12 Jun 1995, John Schneiderman wrote: > What is "minimum divergence times for sister-groups"? If, for example, the oldest fossil from one taxon is dated at 100Ma and the oldest from its sister group at 150Ma, the groups must have diverged at least 150MYA and so are both at least 150Ma old. It is much harder to generate upper age limits. Bill Adlam