Hi, Mr. Jack.
Actually, a little bit more can be said. I have composed a graphicthat shows two scenarios, both of which imply that the members of Bilateria are more closely related to each other than they are to any other group, and that sponges (Porifera) and jellyfish (Cnidaria) are both more closely related to Bilateria than either are to comb jellies (Ctenophora):
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However, there is a subtle difference: in scenario 1, jellyfish are more closely related to Bilateria than to sponges, while in scenario 2 jellyfish and sponges are more closely related to each other than either are to Bilateria.
According to the graphic that I have already posted, the authors of the paper chose scenario 2 as their preferred scenario; you'll see that members of Porifera and Cnidaria share a common node that is not shared with the other groups.
Now, I haven't read the paper yet (I haven't yet made it to the library -- I'm also going to see whether I can scam a copy of the paper for free before I resign myself to paying for it), so it is possible that in the paper the authors caution that their data doesn't rule out scenario 1 (or a third scenario where Porifera is more closely related to Bilateria than they are to Cnidaria). I'm just going by the graphic.
So, according to this scenario, there was a hypothetical ancestor, A, to all extant animals. A then split into two reproductively isolated populations, one of which evolved into the comb jellies, and the other which evolved into B'. B' then split into two isolated populations, one of which evolved into the ancestor of the Bilateria, and the other which evolved into D. Finally, D was the ancestor of sponges and jellyfish.
Speaking personally, I find few things more awesome than contemplating this vast and majestic process of evolution, the ebb and flow of successive biotas through geological time. Creationists and others who cannot for ideological or religious reasons accept the fact of evolution miss out a great deal, and are left with a claustrophobic little universe in which nothing happens and nothing changes.
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M. Alan Kazlev