The following is an illustration rom my book of the phylogenetic tree of 6 animal phyla (the red stuff is mine):
I think what's causing some confusion is that there are no names/years at the circled nodes.
My first question is, was there an actual population between nodes (ex.) 2 and 3?
I would like to check if my understanding of the tree is correct:
Before node 1, there was a population which split into two populations: Porifera and the population between nodes 1 and 2 which we will call population 1-2. This population is unnamed on the diagram, either because we don't have a name for it, or because members of that population no longer exist, or to keep the diagram simplified.
Next, after some millions of years, population 1-2 split into the Cnidarians and population 2-3. Etc.
Is my understanding correct?
Thank you very much.