Study: Chicxulub Asteroid Wiped Out Obamadon and Many Other Cretaceous Lizards, Snakes

A new study published online in the Proceedings of the National Academy of Sciences shows that the Chicxulub asteroid collision, widely thought to have killed the dinosaurs, led to a devastating mass extinction of snakes and lizards, including seven newly identified lizard species and two snakes.

In the foreground, the carnivorous lizard Palaeosaniwa stalks a pair of hatchling Edmontosaurus as the snake Cerberophis and the lizard Obamadon look on. In the background, an encounter between T. rex and Triceratops (Carl Buell)

“The asteroid event is typically thought of as affecting the dinosaurs primarily,” explained Dr Nicholas Longrich of the Yale’s Department of Geology and Geophysics and lead author on the study. “But it basically cut this broad swath across the entire ecosystem, taking out everything. Snakes and lizards were hit extremely hard.”

Earlier studies have suggested that some snake and lizard species extinct after the asteroid struck Earth 65.5 million years ago. But the new study argues that consequences of the collision were far more serious for snakes and lizards than previously understood. “As many as 83 percent of all snake and lizard species died off,” researchers said, “and the bigger the creature, the more likely it was to become extinct, with no species larger than one pound surviving.”

The results are based on a detailed examination of previously collected snake and lizard fossils covering a territory in western North America. The authors examined 21 previously known species and also identified seven new lizards – Obamadon gracilis, Pariguana lancensis, Tripennaculus, Socognathus brachyodon, Lonchisaurus trichurus, Cemeterius monstrosus, Lamiasaurus ferox – and two snake species.

They found that a remarkable range of reptile species lived in the last days of the dinosaurs. Some were tiny lizards. One snake was the size of a boa constrictor, large enough to take the eggs and young of many dinosaur species. Iguana-like plant-eating lizards inhabited the southwest, while carnivorous lizards hunted through the swamps and flood plains of what is now Montana, some of them up to six feet long.

Fossil dentary of the newly identified lizard Obamadon gracilis (Nicholas Longrich et al)

The scientists then conducted a detailed analysis of the relationships of these reptiles, showing that many represented archaic lizard and snake families that disappeared at the end of the Cretaceous, following the asteroid strike. One of the most diverse lizard branches wiped out was the Polyglyphanodontia. This broad category of lizards included up to 40 percent of all lizards then living in North America.

In reassessing previously collected fossils, they came across an unnamed species and called it Obamadon gracilis. “It is a small polyglyphanodontian distinguished by tall, slender teeth with large central cusps separated from small accessory cusps by lingual grooves,” the team wrote.

“The genus name refers to Barack Hussein Obama and odon (tooth in Greek), in reference to the tall, straight teeth, and the manner in which Mr Obama has acted as a role model of good oral hygiene for the world.”

“The creature likely measured less than one foot long and probably ate insects,” Dr Longrich explained. “No one should impute any political significance to the decision to name the extinct lizard after the recently re-elected U.S. president. We’re just having fun with taxonomy.”

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Bibliographic information: Nicholas Longrich et al. Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary. PNAS, published online before print December 10, 2012; doi: 10.1073/pnas.1211526110