occurs when the fossilization potential of one group relative to that of another group changes through time. For example, lingulide brachiopods had a lower fossilization potential than articulate brachiopods, but only in the early Paleozoic. This has changed through time, governed by changes in bathymetry and lateral shifts in lithofacies associated with basin evolution. By the Middle Ordovician, articulates had diversified to become important components of all marine environments except the deep basin; inarticulates were most important in offshore and basinal settings. By moving away from the main taphonomic window, the inarticulates sacrificed their fossilization potential whilst not necessarily decreasing their biological diversity. Global megabias A global megabias is one that occurs over the whole world, though not necessarily in all depositional environments. There are numerous documented examples of this, many of which concern the Cambrian explosion and the Ediacaran fauna, both divisive subjects within the paleobiological community. Darwin commented on the Cambrian explosion, it being a great problem in his eyes, and speculated that it may be due to an increased propensity for preservation in the Cambrian and a reduced potential beforehand. Cambrian reduction of phosphatization Many fossils, such as the Cambrian Small Shelly Fauna (SSF), are preserved through secondary phosphatization. Such preservation can boost the diversity estimates in three ways: By preserving fossils that might otherwise be destroyed By preserving fine anatomical structures that enhance taxonomic resolution. Small anatomical details will show differences between two specimens that would otherwise be lumped within the same group; in this way, an inflated measure of diversity is given By allowing easy collection. Phosphatized organisms are incredibly easily to extract by acid maceration, allowing large numbers of specimens to be collected with ease. The number of phosphatic facies deposits decreases significantly from the early- to mid-Cambrian. Most probably, this is the cause for the pattern of SSF diversity decline after the Botomian extinction. Whilst there may well have been a significant extinction worldwide of small shelly fossils, a significant decrease in the abundance of phosphatized facies may have caused the decline in SF diversity to appear much more severe than it really was. Overabundance of Konservat-Lagerstätten It has been noted after the last 20 years that Exceptional Faunas, a particular class of Konservat-Lagerstätten exemplified by Burgess shale deposits, are statistically overabundant considering their age and style of preservation. This problem is also known as the "Post-Cambrian closure of the deep-water slope-basin taphonomic