title: When and how did the terrestrial mid-Permian mass extinction occur? Evidence from the tetrapod record of the Karoo Basin, South Africa.
abstract: A mid-Permian (Guadalupian epoch) extinction event at approximately 260 Ma has been mooted for two decades. This is based primarily on invertebrate biostratigraphy of Guadalupian-Lopingian marine carbonate platforms in southern China, which are temporally constrained by correlation to the associated Emeishan Large Igneous Province (LIP). Despite attempts to identify a similar biodiversity crisis in the terrestrial realm, the low resolution of mid-Permian tetrapod biostratigraphy and a lack of robust geochronological constraints have until now hampered both the correlation and quantification of terrestrial extinctions. Here we present an extensive compilation of tetrapod-stratigraphic data analysed by the constrained optimization (CONOP) algorithm that reveals a significant extinction event among tetrapods within the lower Beaufort Group of the Karoo Basin, South Africa, in the latest Capitanian. Our fossil dataset reveals a 74-80% loss of generic richness between the upper Tapinocephalus Assemblage Zone (AZ) and the mid-Pristerognathus AZ that is temporally constrained by a U-Pb zircon date (CA-TIMS method) of 260.259 ± 0.081 Ma from a tuff near the top of the Tapinocephalus AZ. This strengthens the biochronology of the Permian Beaufort Group and supports the existence of a mid-Permian mass extinction event on land near the end of the Guadalupian. Our results permit a temporal association between the extinction of dinocephalian therapsids and the LIP volcanism at Emeishan, as well as the marine end-Guadalupian extinctions.
authors.affiliation: Evolutionary Studies Institute, School of Geosciences, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa michael.day@wits.ac.za.
authors.forename: Michael O
authors.initials: MO
authors.lastname: Day
authors.affiliation: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Jahandar
authors.initials: J
authors.lastname: Ramezani
authors.affiliation: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Bowring
authors.affiliation: Department of Earth Sciences, University of California, Riverside, CA 92521, USA.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Sadler
authors.affiliation: Department of Paleobiology, National Museum of Natural History, Washington, DC 20013-7012, USA.
authors.forename: Douglas H
authors.initials: DH
authors.lastname: Erwin
authors.affiliation: Evolutionary Studies Institute, School of Geosciences, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa.
authors.forename: Fernando
authors.initials: F
authors.lastname: Abdala
authors.affiliation: Evolutionary Studies Institute, School of Geosciences, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa.
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Rubidge
mesh_terms: D000818:Animals; D044822:Biodiversity; D053476:Extinction, Biological; D005580:Fossils; D012104:Reptiles; D013019:South Africa
keywords: Guadalupian; Karoo; Permian; U–Pb geochronology; biostratigraphy; tetrapod extinction