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Vertebrates and tectonics

Paleontologists suggested some new twists on tectonics and ecosystems at the annual meeting of the Society of Vertebrate Paleontology (SVP), held mid-October in St. Paul, Minn. Their ideas might offer answers to some key conundrums regarding extinction, speciation and the global distribution of vertebrate species. (For the full story online, read the WebExtra.)

Malcolm McKenna, a paleobiologist affiliated with the University of Wyoming and the University of Colorado Museum, presented his ideas on the so-called Lake Arctica scenario, when a proto-Iceland connected North America to Europe, 56 million years ago. “Everybody has assumed the only bridge connecting the old world to the new was through Alaska,” McKenna says. “Not so, 55 to 55.5 million years ago: You could walk from New Mexico to Paris, without changing latitude.”

That land bridge may have connected species from the continents, but it also blocked circulation between the Arctic and the newly spreading Atlantic, affecting salinity and water temperature of the Arctic Ocean. When the land bridge broke, changes in ocean temperature could have destabilized methane clathrates in the Arctic, leading to the very short but intense global warming at the Paleocene-Eocene boundary.

McKenna’s ideas might explain some odd patterns, says William Clyde, a mammal specialist at the University of New Hampshire in Durham, including a concurrent big extinction of benthic foraminifera, a major introduction of new land vertebrate species and warm temperatures at high latitudes. But Lance Grande, an evolutionary biologist at the Chicago Field Museum, questions whether the idea is any more probable than other explanations for these events, including genetically related fossil fish found in both Asia and North America.

Naomi Lubick


For more details on this, as well as new findings on how tectonics and climate can serve as predictors for the genetic variation and extinction of vertebrate species, visit the full Web Extra, “Vertebrates and tectonics.”

Check out past Web Extras on the online archive at: www.geotimes.org/WebextraArchive.html.

Slow climate changes in a large floodplain in Pakistan, represented by Miocene sediments pictured here, gave mammals refuge — and low rates of speciation and extinction. Image courtesy of Catherine Badgley.

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