使恐龙灭绝的小行星同时重创蛇蜥类

The asteroid¹（小行星） collision widely thought to have killed the dinosaurs³ also led to extreme devastation⁴ among snake and lizard⁵ species, according to new research -- including the extinction⁶ of a newly identified lizard Yale and Harvard scientists have named Obamadon gracilis. "The asteroid event is typically thought of as affecting the dinosaurs primarily," said Nicholas R. Longrich, a postdoctoral associate with Yale's Department of Geology and Geophysics and lead author of the study. "But it basically cut this broad swath across the entire ecosystem⁷, taking out everything. Snakes and lizards⁸ were hit extremely hard."

 

The study was scheduled for online publication the week of Dec. 10 in the Proceedings⁹ of the National Academy of Sciences.

 

Earlier studies have suggested that some snake and lizard species (as well as many mammals, birds, insects and plants) became extinct after the asteroid struck Earth 65.5 million years ago, on the edge of the Yucatan Peninsula. But the new research argues that the collision's consequences were far more serious for snakes and lizards than previously¹⁰ understood. As many as 83 percent of all snake and lizard species died off, the 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 detailed¹¹ examination of previously collected snake and lizard fossils covering a territory in western North America stretching from New Mexico in the southwestern United States to Alberta, Canada. The authors examined 21 previously known species and also identified nine new lizards and snakes.

 

They found that a remarkable¹² range of reptile¹³ 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 dinosaur² species. Iguana-like plant-eating lizards inhabited the southwest, while carnivorous（食肉的） lizards hunted through the swamps and flood plains of what is now Montana, some of them up to six feet long.

 

"Lizards and snakes rivaled the dinosaurs in terms of diversity, making it just as much an 'Age of Lizards' as an 'Age of Dinosaurs,'" Longrich said.

 

The scientists then conducted a detailed analysis of the relationships of these reptiles¹⁴, showing that many represented archaic¹⁵ 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, according to the researchers. In reassessing previously collected fossils, they came across an unnamed species and called it Obamadon gracilis. In Latin, odon means "tooth" and gracilis means "slender."

 

"It is a small polyglyphanodontian distinguished¹⁶ by tall, slender teeth with large central cusps separated from small accessory cusps by lingual¹⁷ grooves," the researchers write of Obamadon, which is known primarily from the jaw¹⁸ bones of two specimens¹⁹. Longrich said the creature likely measured less than one foot long and probably ate insects.

 

He said no one should impute²⁰ 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（分类学）."

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