So what say you Tranquility, are these listed species the "Original Kinds"?
They are the only things we find in the cambrian layers, and even up into the Sil/Ord Devonian and Carboniferous layers.
They must be the original "kinds" as we don't find any others in all the strata. In other words, the original primitive gastropods, trilobites, etc. were the original creatures created on creation week. The "Tree of Life" was actually probably some sort of a simple valved polyp, as fronded ferns and other primitive treelke plants don't appear until the devonian, and angiosperms until the Jurassic.
My guess would be that God created some of the kinds (like jellyfish, pikia, bryzoa, crinoids) during creation week, then waited for the flood to create the rest.
Then as the flood was raging, he created the rest of the kinds in mid air, and dropped them in the water on the first, second, third, day etc. so they would drown and settle to the bottom in just the proper order.
He also made sure that each of the new species he created during the flood were just different enough from those the day before that they could be put together in some sort of treelike relationship later on to fool the scientists (godless heathens that they are).
Anyhow.. that's my own personal theory of kinds and how they managed somehow to get in the layers they are in now in the order they are in. It almost makes sense.