Carboniferous-earliest Permian marine biodiversification event (CPBE) during the Late Paleozoic Ice Age

Abstract The Late Paleozoic Ice Age (LPIA) is a critical interval for marine ecosystems when marine fauna was viewed to have experienced a second-order mass extinction and a “sluggish” evolution with low origination and extinction rates. However, our recent study discovered that this ice age was accompanied by a rapid, significant increase of marine fauna species and genus richness. Here, we present the precise details of this biodiversification process, including the high-resolution species and genus richness changes, to decipher its timing and magnitude, as well as the divergent species richness changes of major marine clades during the event. The temporal resolutions are as high as 36 kyr and 21 kyr for the Carboniferous and Permian, respectively, and as a result provide the ability of uncovering the process in great detail. This marine biodiversification event lasted 41.2 Myr from the middle Visean of the Carboniferous to the late Asselian of the Permian with species number increased 246%, therefore named Carboniferous-earliest Permian Biodiversification Event (CPBE). CPBE includes a slow increase episode in the middle Visean to early Bashkirian and a main radiation episode of Bashkirian to Asselian. The radiation pattern is most distinct in fusulinid foraminifera while brachiopods species also kept the trend of increase. However, nektonic conodonts and cephalopods both exhibit stepwise drops during this time interval. These biotic changes might relate to the marine environmental shifts, such as suppressed marine circulation and fragmented niches, mainly raised by the Rheic Ocean closure.