New Dates from New Mexico: The Last Dinosaurs in North America

Scientists found many dinosaur fossils in northwestern New Mexico. The bones come from the Naashoibito Member in the San Juan Basin. Geologists dated the rocks and found ages between 66.4 and 66 million years old. These dates place the animals very close to the time of the asteroid impact.

The fossils include large long-necked dinosaurs such as Alamosaurus and other species. Researchers say these dinosaur communities were different from those in the north. They lived in thriving ecosystems until the asteroid hit. After the impact, dinosaurs disappeared and mammals later grew.