I see the last thread was shut down because people can't seem to be civil with each other. So here I am reposting something I posted in the "Explain the fossil record without evolution" thread. It deals with the various mechanisms proposed by Floodists to explain the stratification of the fossil record. The listing of these mechanisms was the most substantive response to the OP in that thread and the user who posted it declined to provide a real response to my coral post, so perhaps in this thread either he or another Floodist will make a real response in this new thread.
And let's try not to be d**ks to each other. Anyway...
Proposed mechanisms:
1. Differential escape
2. Hydrologic sorting
3. Selective preservation
4. a) ecological zonation
b) biogeographic zonation
5. Chance
There are a few quick examples of organisms whose positions in the fossil record are not readily explained by the mechanisms proposed. Let's look at coral. Specifically, let's look at two major groups of coral, Rugosa and Scleractinia. The former appears in the Ordovician whereas the later doesn't show up until a couple hundred million years later in the Triassic. Corals are sessile so obviously we can immediately dismiss the differential escape mechanism as an explanation for why rugosans appear in the rock record long before the vast majority of scleractinians do and vanish shortly (geologically speaking) after they appear.
What about hydrologic sorting? Let's take a look at a couple examples of the two groups:
You can see pretty clearly that scleractinians and rugosans overlap significantly in their morphologies, so hydrological sorting would not differentiate between the two groups based on shape alone. You could make an argument that density is the deciding factor because scleractinians tend to be more porous and rugosans more dense, thus one might argue that the more dense rugosans should be expected to appear lower in section. All things being equal this would make sense, but it fails to account for why we don't find large scleractinians appearing in the record prior below small rugosans. A scleractinian colony 2m in diameter is still going to settle out before a 8cm rugosan colony. So in the end hydrological sorting fails to explain why rugosans always appear before scleractinians.
What about selective preservation? While rugosans and scleractinians have skeletons composed of roughly the same material, the calcite that composes rugosan skeletons is somewhat more easily preserved than the aragonite comprising the scleractinian skeleton. Perhaps one might argue that this is why scleractinians are not found lower in section. But this does not explain why rugosans all but disappear near the Permian boundary. So selective preservation fails to explain the arrangement of these two groups.
What about biogeographic and ecological zonation? We know that modern scleractinians, depending on the type, inhabit both warm, shallow, sunlit waters as well as cold, deep, dark waters. They inhabit every ocean on the planet. The same is true of their fossil counterparts. And as you can see in these Excel spreadsheets (actually just screencaps, I can't figure out how to upload the actual xls file), scleractinians and rugosans inhabited the same environments in the same areas of the world. This means that ecological and biogeographic zonation also fail to explain why rugosans always appear in the rock record prior to scleractinians.
That leaves us with random chance. This seems like a weak argument to me, but let's look at the numbers. If you look at the spreadsheet you will see that there are 35,248 occurrences of scleractinians in the Palaeobiological database (PBDB) and 175,857 rugosans. And this is by no means a complete count; the PBDB only contains records that researchers and institutions have uploaded. Even so, these numbers make it very unlikely that pure chance caused rugosans and scleractinians to be arranged as they are.
And let's try not to be d**ks to each other. Anyway...
Proposed mechanisms:
1. Differential escape
2. Hydrologic sorting
3. Selective preservation
4. a) ecological zonation
b) biogeographic zonation
5. Chance
There are a few quick examples of organisms whose positions in the fossil record are not readily explained by the mechanisms proposed. Let's look at coral. Specifically, let's look at two major groups of coral, Rugosa and Scleractinia. The former appears in the Ordovician whereas the later doesn't show up until a couple hundred million years later in the Triassic. Corals are sessile so obviously we can immediately dismiss the differential escape mechanism as an explanation for why rugosans appear in the rock record long before the vast majority of scleractinians do and vanish shortly (geologically speaking) after they appear.
What about hydrologic sorting? Let's take a look at a couple examples of the two groups:
You can see pretty clearly that scleractinians and rugosans overlap significantly in their morphologies, so hydrological sorting would not differentiate between the two groups based on shape alone. You could make an argument that density is the deciding factor because scleractinians tend to be more porous and rugosans more dense, thus one might argue that the more dense rugosans should be expected to appear lower in section. All things being equal this would make sense, but it fails to account for why we don't find large scleractinians appearing in the record prior below small rugosans. A scleractinian colony 2m in diameter is still going to settle out before a 8cm rugosan colony. So in the end hydrological sorting fails to explain why rugosans always appear before scleractinians.
What about selective preservation? While rugosans and scleractinians have skeletons composed of roughly the same material, the calcite that composes rugosan skeletons is somewhat more easily preserved than the aragonite comprising the scleractinian skeleton. Perhaps one might argue that this is why scleractinians are not found lower in section. But this does not explain why rugosans all but disappear near the Permian boundary. So selective preservation fails to explain the arrangement of these two groups.
What about biogeographic and ecological zonation? We know that modern scleractinians, depending on the type, inhabit both warm, shallow, sunlit waters as well as cold, deep, dark waters. They inhabit every ocean on the planet. The same is true of their fossil counterparts. And as you can see in these Excel spreadsheets (actually just screencaps, I can't figure out how to upload the actual xls file), scleractinians and rugosans inhabited the same environments in the same areas of the world. This means that ecological and biogeographic zonation also fail to explain why rugosans always appear in the rock record prior to scleractinians.
That leaves us with random chance. This seems like a weak argument to me, but let's look at the numbers. If you look at the spreadsheet you will see that there are 35,248 occurrences of scleractinians in the Palaeobiological database (PBDB) and 175,857 rugosans. And this is by no means a complete count; the PBDB only contains records that researchers and institutions have uploaded. Even so, these numbers make it very unlikely that pure chance caused rugosans and scleractinians to be arranged as they are.
