GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 247-3
Presentation Time: 8:30 AM


LUCAS, Spencer G., New Mexico Museum of Natural History and Science, 1801 Mountain Road N.W, Albuquerque, NM 87104

Identification of Phanerozoic mass extinctions on land has been confounded by incorrect correlations, the compiled correlation effect, not recognizing taphonomic filters and/or misunderstanding biodiversity changes recorded by the nonmarine fossil record. With regard to the so-called “Big 5 mass extinctions” of marine invertebrates, only the end-Cretaceous extinction may be associated with a coeval nonmarine mass extinction. Not enough lived on land or we don’t know enough about life on land during the Late Ordovician to identify nonmarine extinctions coeval with the two Late Ordovician marine extinctions. A convincing case also cannot be made for mass extinctions on land coeval with the marine extinctions of the Late Devonian. Late Devonian land plant extinctions are part of a long interval of low origination and high extinction rates, whereas the tetrapod record is inadequate to identify any mass extinctions. There were no mass extinctions of land plants, arthropods or tetrapods across the Permo-Triassic boundary. A case can be made for coeval plant/tetrapod extinctions and the end-Guadalupian marine extinctions, so this may be the first coeval land-sea mass extinction, but further research is needed. The last ~ 5 million years of the Triassic were a time of low origination and high extinction rates on land and in the seas; there was no single end-Triassic mass extinction in either realm. The end-Cretaceous provides the strongest case for coeval land-sea mass extinctions, but there is no mass extinction of land plants, and the tetrapod extinction is inexplicably selective, so whether the nonmarine extinction was a mass extinction is worth questioning. Most who have posited nonmarine mass extinctions have failed to answer the question: if there is no mass extinction of land plants, what brings down the rest of the terrestrial biota? Furthermore, this is often overlooked: the nonmarine biota, through various devices, including dormant seeds and larval stages, and fleeing, burrowing and other means of sheltering, is more resilient than the marine biota to most of the proposed triggers of mass extinctions. If you live in the sea, any change in ocean water chemistry cannot be readily escaped, so such changes have the potential to trigger a devastating diversity collapse. On land, you have many ways to escape those triggers.