decision needed: treating taxa not in synth tree

Currently we have lists that match OTT but sometimes the taxa are not in the tree if they are extinct or incertae sedis.  

So, a user could have a nice list with 10 taxa from the portal itself, as in #330, but they are all extinct so no tree can be retrieved.  

Consider the sources of this problem, and how to deal with it.  Make a recommendation.