Updating the fungal infection-mammalian selection hypothesis at the end of the Cretaceous Period
Year: 2020
Type: article
Abstract: In 2005, one of us proposed that a fungal bloom at the end of the Cretaceous Period would have favored the selection of the endothermic mammals over ectothermic reptiles, which eventually led to the great mammalian radiation and the replacement of the Cretaceous reptilian megafauna with the mammalian megafauna of the Tertiary or Paleogene Period [1].This idea, which we now name the "fungal infection-mammalian selection" (FIMS) hypothesis, suggested a new explanation for how the mammals came to replace reptiles as the dominant large animals after the Cretaceous Period [2], which ended 66 million years ago with a planetary cataclysm known as the Cretaceous-Paleogene extinction event.At the time, this extinction event was attributed to volcanism, a bolide impact, or some combination of both.In the ensuing decade and a half since FIMS was first proposed, considerable progress was made in understanding the events following the cataclysm at the end of the Cretaceous Period, which provide the opportunity to add refinements to this hypothesis.For example, in 2005, there was uncertainty on the temporal relationship between the bolide impact and the mass extinction event, with some estimates placing it 300,000 years earlier [3].Today there is a growing consensus for a temporal and causative relationship between a bolide impact at Chicxulub, Mexico, in the Yucatan peninsula and the mass extinction event at the end of the Cretaceous Period [4].This together with a greater appreciation of the planetary effects following this cataclysm [5] allow refinements and updates to the FIMS hypothesis. The FIMS hypothesisThe geologic record is divided into periods of which the Cretaceous is that time between the Jurassic and Paleogene that spanned a time from 145 to 66 million years ago.The Cretaceous Period came to an abrupt end with the Cretaceous-Paleogene extinction event, which saw the demise of nonavian dinosaurs and many ancient species.How did mammals become the dominant large animals in the Paleogene and later periods?A widely accepted view is that the cataclysm that marked the end of the Cretaceous Period killed off the dinosaurs creating an ecologic opening for the mammals.However, that view falters in explanative power when one considers that many species of reptiles also survived the calamity, and, given that this group of animals possesses certain advantages over mammals, it does not explain why the survivors failed to usher a second reptilian age.In this regard, the mammalian lifestyle is significantly more expensive than that of ectothermic reptiles, with field metabolic rates that are 12 to 20 times higher [6], requiring consumption of much larger amounts of food for homeostasis.The FIMS hypothesis posits that a fungal bloom following the cataclysm at the end of the
Source: PLoS Pathogens
Authors: Arturo Casadevall, Chris Damman
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,500
OpenAlex ID: W3043597256