The standard approach to looking at fossils in the geological column is to assume that lower is older.
Since the geologic column represents millions of years of Earth's history, then obviously the fossils in each of the layers must be the same age as the layer in which they are found.
This is because large areas include a subset of species not found elsewhere. [These features are consistent with the hypothesis of] "isolated habitat 'islands'." Using this line of reasoning, one might reasonable hypothesize that trilobites appear in the fossil record before crabs and lobsters at least party because of the relative abundance of trilobites compared to crabs and lobsters.
Therefore, the nested subset pattern of species distribution in space is thought to reflect the gradient in abundance among species (Gaston, 1996; Leitner and Rosenzweig, 1997; Maurer, 1999). This hypothesis is at least plausible given the author's conclusion that, "Species identities and their relative abundances are non-random properties of communities that persist over long periods of ecological time and across geographic space.
Some habitats are clearly more susceptible to the preservation of fossils.
If those specific habitats are not occupied by a particular kind of creature, it may not be preserved in the fossil record even though it is still alive and well in some other habitat.
So, let's take another look at the available evidence and see if any other possibilities present themselves.
Doesn't this fact support the notion that simple organisms evolved into more and more complex organisms over time, with the more complex organisms buried and fossilized above the earlier and simpler life forms?
Then they suddenly disappear from the fossil record some 80 million years ago only to reappear alive an well swimming around in oceans today.
Clearly, some types of coelacanths lived in habitats that did not lend themselves to fossilization while others did.