Tuesday, December 11, 2012

[Paleontology • 2012] Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary | Obamadon gracilis, Lonchisaurus trichurus & Cerberophis robustus

The carnivorous lizard Palaeosaniwa stalks a pair of hatchling Edmontosaurus dinosaurs as the snake Cerberophis looks on from above, and the lizard Obamadon watches from below. Meanwhile, in the background, a Tyrannosaurus rex encounters a Triceratops troop while an asteroid streaks down to Earth.
Art: Carl Buell 

The Cretaceous–Paleogene (K-Pg) boundary is marked by a major mass extinction, yet this event is thought to have had little effect on the diversity of lizards and snakes (Squamata). A revision of fossil squamates from the Maastrichtian and Paleocene of North America shows that lizards and snakes suffered a devastating mass extinction coinciding with the Chicxulub asteroid impact. Species-level extinction was 83%, and the K-Pg event resulted in the elimination of many lizard groups and a dramatic decrease in morphological disparity. Survival was associated with small body size and perhaps large geographic range. The recovery was prolonged; diversity did not approach Cretaceous levels until 10 My after the extinction, and resulted in a dramatic change in faunal composition. The squamate fossil record shows that the end-Cretaceous mass extinction was far more severe than previously believed, and underscores the role played by mass extinctions in driving diversification.

Keywords: evolution, adaptive radiation

Longrich, N.R.,Bhullar, Bhart-Anjan S. and Gauthier, J.A. 2012. Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary. PNAS. 

Yale scientists name Obamadon, a slender-jawed lizard after the President http://bo.st/VvB6D9 via @BostonDotCom
Ancient lizard that died out with the dinosaurs named after Obama http://nbcnews.to/YVtkKj  via @cosmiclog

Obama the lizard: Yale study weighs in: http://www.yalealumnimagazine.com/blog/?p=17247