• Sierra del Carmen

    Big Bend

    National Park Texas

Pterosaur Extinction

 

Pterosaur Extinction
Not only was Quetzalcoatlus the one of largest of the pterosaurs, it was the last. It was found in the rocks of the latest, uppermost Cretaceous period, just before the beginning of the Tertiary period 65 million years ago. This border between major time periods is known as the Cretaceous-Tertiary boundary, or K-T boundary for short, and marks the great extinction at the end of the Cretaceous. This mass extinction episode wiped out dinosaurs, pterosaurs, marine reptile groups such as plesiosaurs, ichthyosaurs, and mosasaurs, and numerous marine invertebrate species such as ammonites. The K-T boundary marks the end of the Mesozoic era, the Age of Reptiles, and denotes the beginning of the Cenozoic era, the Age of Mammals.

The K-T boundary has received intense scientific study in recent years as researchers try to understand the changes between the time periods. Big Bend’s rocks are important to this study because the K-T boundary is well preserved, is clearly exposed, and is one of the southernmost exposures of terrestrial sedimentary rocks of that time period. On a geologic scale, Big Bend is relatively close to the well-publicized Yucatan meteor impact point, which has recently gained favor as an explanation for the abrupt changes seen at the K-T boundary.

It is important to understand that even if the Yucatan meteor is shown to be the coup de grace that finished off many Mesozoic species, it is only a small part of the story. Indeed, the fossil record clearly shows that these animals were gradually declining in diversity, with numerous species going extinct during the Upper Cretaceous, over millions of years. During this time the world’s climate was changing as shallow seas were draining, mountains were being built, temperatures were cooling, and perhaps wind speeds were increasing. Although a meteor may have finished things with a bang, the real culprit in most of the Cretaceous extinctions was long-term global climate change.

Did You Know?

CHANGE

Air temperature changes by five degrees for every 1,000 feet of elevation you gain or lose; temperatures in the High Chisos Mountains in Big Bend National Park can be 30 degrees cooler than temperatures along the Rio Grande. More...