Recent findings have upended the long-standing belief that dinosaur populations were in decline prior to the asteroid impact that led to their extinction. A fossil site located in New Mexico, known as the Naashoibito site, has offered crucial evidence indicating that dinosaurs were flourishing just before this catastrophic event.
The fossils at the Naashoibito site, which include the massive Alamosaurus, date back approximately 340,000 years before the asteroid struck off the coast of Mexico”s Yucatan Peninsula, marking the end of the Cretaceous Period around 66 million years ago. The study, which utilized two dating methods, has reignited discussions among paleontologists regarding the age of these fossils.
Paleontologist Dan Peppe from Baylor University and one of the study”s authors noted, “The age of the Naashoibito dinosaur faunas has been controversial for a long time, with some researchers suggesting that it was as much as 70 million years old, while others have suggested that it sampled the latest Cretaceous.” This research provides new insights that contradict the prevailing narrative of a global decline in dinosaur populations before the impact.
The diverse fossil assemblage at the Naashoibito site, located near Farmington, New Mexico, includes numerous species adapted to various ecological niches. Among them, the Alamosaurus stood out as the largest of the plant-eating dinosaurs, reaching over thirty tons and approximately one hundred feet in length. Other notable dinosaurs found at the site include duckbilled dinosaurs, armored dinosaurs, and the fearsome apex predator Tyrannosaurus, as well as the horned dinosaur Torosaurus.
The research compared these fossils to those from the Hell Creek formation, which spans regions in Montana, North Dakota, South Dakota, and Wyoming. This comparison indicated that the dinosaur communities in the southern United States differed significantly from those in the north. While some species like Tyrannosaurus and Torosaurus appeared in both regions, the southern community boasted a variety of sauropods, including the common presence of Alamosaurus, which were absent in the northern regions.
Peppe further explained, “This shows that dinosaurs were not a single homogeneous community spread across North America that was prone to extinction. Instead, they were diverse and abundant leading up to the end of the Cretaceous.”
Steve Brusatte, a paleontologist from the University of Edinburgh and co-author of the study, emphasized the adaptability of dinosaurs. He stated, “They were doing what dinosaurs had been doing for over 150 million years, adapting to their local conditions, dividing up niches in the food chain, varying in size and shape and diet and exhibiting rich diversity across the landscape. There is no sign that these dinosaurs were in any trouble, or that anything unusual was happening to them, or that they were in any type of long-term decline.”
Interestingly, the Alamosaurus, known as the last sauropod dinosaur from North America, thrived in warm climates, with fossils also found in Texas and Utah. Brusatte remarked, “Nothing illustrates how dinosaurs were thriving up to the very end more than the fact that Alamosaurus, one of the biggest dinosaurs ever – in fact, one of the very biggest animals to ever live on land in the entire history of the Earth – was there to witness the asteroid.” He vividly described the scene, saying, “I can imagine the scene: one minute, a jet plane-sized dinosaur was shaking the ground as it walked, the next minute the whole Earth was shaking with the energy unleashed by the asteroid.”
