Barriers to finding that important fossil

Carl Zimmer has an interesting post about the discovery of a large filter feeding fish. Filter feeding today is used by several species of shark and also more famously, whales. In the search for fossils there are many barriers to finding those important fossils that illustrate some aspect of evolution. It is very rare that fossils are formed and only a small area has actually been seached are two that we could name. Here is another barrier. The fossil was actually found, but its significance wasn't understood at the time and it was put into storage. Well Matt Friedman has been scouring museum collections and has plugged a 80 million year hole in the evolution of filter feeding fish with several specimans that had been gathering dust.