Evidence from South Africa for a protracted end-Permian extinction on land

Earth’s largest biotic crisis occurred during the Permo–Triassic Transition (PTT). On land, this event witnessed a turnover from synapsid- to archosauromorph-dominated assemblages and a restructuring of terrestrial ecosystems. However, understanding extinction patterns has been limited by a lack of...

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Published in:	Proceedings of the National Academy of Sciences - PNAS Vol. 118; no. 17; pp. 1 - 8
Main Authors:	Viglietti, Pia A., Benson, Roger B. J., Smith, Roger M. H., Botha, Jennifer, Kammerer, Christian F., Skosan, Zaituna, Butler, Elize, Crean, Annelise, Eloff, Bobby, Kaal, Sheena, Mohoi, Joël, Molehe, William, Mtalana, Nolusindiso, Mtungata, Sibusiso, Ntheri, Nthaopa, Ntsala, Thabang, Nyaphuli, John, October, Paul, Skinner, Georgina, Strong, Mike, Stummer, Hedi, Wolvaardt, Frederik P., Angielczyk, Kenneth D.
Format:	Journal Article
Language:	English
Published:	United States National Academy of Sciences 27-04-2021
Series:	From the Cover
Subjects:	Abundance Biological Sciences Disasters Endangered & extinct species Environmental changes Extinction Fossils Mass extinctions Oceans Permian Physical Sciences Stratigraphy Taxa Terrestrial ecosystems Terrestrial environments Triassic South Africa Karoo Permo-Triassic Diversity dynamics Karoo Basin Lystrosaurus Mass extinction
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Summary:	Earth’s largest biotic crisis occurred during the Permo–Triassic Transition (PTT). On land, this event witnessed a turnover from synapsid- to archosauromorph-dominated assemblages and a restructuring of terrestrial ecosystems. However, understanding extinction patterns has been limited by a lack of high-precision fossil occurrence data to resolve events on submillion-year timescales. We analyzed a unique database of 588 fossil tetrapod specimens from South Africa’s Karoo Basin, spanning ∼4 My, and 13 stratigraphic bin intervals averaging 300,000 y each. Using samplestandardized methods, we characterized faunal assemblage dynamics during the PTT. High regional extinction rates occurred through a protracted interval of ∼1 Ma, initially co-occurring with low origination rates. This resulted in declining diversity up to the acme of extinction near the Daptocephalus–Lystrosaurus declivis Assemblage Zone boundary. Regional origination rates increased abruptly above this boundary, co-occurring with high extinction rates to drive rapid turnover and an assemblage of short-lived species symptomatic of ecosystem instability. The “disaster taxon” Lystrosaurus shows a long-term trend of increasing abundance initiated in the latest Permian. Lystrosaurus comprised 54% of all specimens by the onset of mass extinction and 70% in the extinction aftermath. This early Lystrosaurus abundance suggests its expansion was facilitated by environmental changes rather than by ecological opportunity following the extinctions of other species as commonly assumed for disaster taxa. Our findings conservatively place the Karoo extinction interval closer in time, but not coeval with, the more rapid marine event and reveal key differences between the PTT extinctions on land and in the oceans.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Edited by Anna K. Behrensmeyer, Smithsonian National Museum of Natural History, Washington, DC, and approved March 2, 2021 (received for review August 12, 2020) Author contributions: P.A.V., R.B.J.B., and K.D.A. designed research; P.A.V., R.B.J.B., and K.D.A. performed research; P.A.V., R.M.H.S., J.B., C.F.K., Z.S., E.B., A.C., B.E., S.K., J.M., W.M., N.M., S.M., N.N., T.N., J.N., P.O., G.S., M.S., H.S., and F.P.W. contributed raw data/analytic tools; R.B.J.B. analyzed data; and P.A.V., R.B.J.B., and K.D.A. wrote the paper.
ISSN:	0027-8424 1091-6490
DOI:	10.1073/pnas.2017045118