Apparently this post did not go through when I sent it earlier on Monday. I don't see it in the DML archive for the 19th. Apologies if some people did get it.
---------- Forwarded message ---------
From: Ben Creisler <bcreisler@gmail.com>
Date: Mon, Apr 19, 2021 at 1:51 PM
Subject: End-Permian extinction on land was protracted based on South African fossils
To: <dinosaur-l@usc.edu>
From: Ben Creisler <bcreisler@gmail.com>
Date: Mon, Apr 19, 2021 at 1:51 PM
Subject: End-Permian extinction on land was protracted based on South African fossils
To: <dinosaur-l@usc.edu>
A new paper:
Mass extinctions permanently altered lifeâs evolutionary trajectory five times in Earthâs history, and the end-Permian extinction was the greatest of these biotic crises. South Africaâs unparalleled fossil record provides a window into mass extinction dynamics on land. We analyze a unique dataset comprising hundreds of precisely positioned tetrapod fossils, identifying a protracted (â1 Ma) extinction. This contrasts with the rapid marine extinction, demonstrating that the effects of biotic crises vary prominently among Earthâs surface environments. We also identify the blooming of âdisaster taxaâ before the main extinction rather than in its aftermath as assumed previously. These changes contributed to breaking the incumbency of previously dominant mammal relatives (synapsids) after the extinction and to the Triassic rise of crocodile- and dinosaur-line archosaurs.
Abstract
Earthâs largest biotic crisis occurred during the PermoâTriassic 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 Africaâs Karoo Basin, spanning ~4 My, and 13 stratigraphic bin intervals averaging 300,000 y each. Using sample-standardized 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 DaptocephalusâLystrosaurus 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.
Earth's biggest mass extinction took ten times longer on land than in the water
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Pia A. Viglietti, Roger B. J. Benson, Roger M. H. Smith, Jennifer Botha, Christian F. Kammerer, Zaituna Skosan, Elize Butler, Annelise Crean, Bobby Eloff, Sheena Kaal, JoÃl Mohoi, William Molehe, Nolusindiso Mtalana, Sibusiso Mtungata, Nthaopa Ntheri, Thabang Ntsala, John Nyaphuli, Paul October, Georgina Skinner, Mike Strong, Hedi Stummer, Frederik P. Wolvaardt, and Kenneth D. Angielczyk (2021)
Evidence from South Africa for a protracted end-Permian extinction on land.
Proceedings of the National Academy of Sciences 118 (17): e2017045118
doi: https://doi.org/10.1073/pnas.2017045118
https://www.pnas.org/content/118/17/e2017045118
Significance
Pia A. Viglietti, Roger B. J. Benson, Roger M. H. Smith, Jennifer Botha, Christian F. Kammerer, Zaituna Skosan, Elize Butler, Annelise Crean, Bobby Eloff, Sheena Kaal, JoÃl Mohoi, William Molehe, Nolusindiso Mtalana, Sibusiso Mtungata, Nthaopa Ntheri, Thabang Ntsala, John Nyaphuli, Paul October, Georgina Skinner, Mike Strong, Hedi Stummer, Frederik P. Wolvaardt, and Kenneth D. Angielczyk (2021)
Evidence from South Africa for a protracted end-Permian extinction on land.
Proceedings of the National Academy of Sciences 118 (17): e2017045118
doi: https://doi.org/10.1073/pnas.2017045118
https://www.pnas.org/content/118/17/e2017045118
Significance
Mass extinctions permanently altered lifeâs evolutionary trajectory five times in Earthâs history, and the end-Permian extinction was the greatest of these biotic crises. South Africaâs unparalleled fossil record provides a window into mass extinction dynamics on land. We analyze a unique dataset comprising hundreds of precisely positioned tetrapod fossils, identifying a protracted (â1 Ma) extinction. This contrasts with the rapid marine extinction, demonstrating that the effects of biotic crises vary prominently among Earthâs surface environments. We also identify the blooming of âdisaster taxaâ before the main extinction rather than in its aftermath as assumed previously. These changes contributed to breaking the incumbency of previously dominant mammal relatives (synapsids) after the extinction and to the Triassic rise of crocodile- and dinosaur-line archosaurs.
Abstract
Earthâs largest biotic crisis occurred during the PermoâTriassic 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 Africaâs Karoo Basin, spanning ~4 My, and 13 stratigraphic bin intervals averaging 300,000 y each. Using sample-standardized 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 DaptocephalusâLystrosaurus 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.
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News:
News:
Earth's biggest mass extinction took ten times longer on land than in the water