Were dinosaurs really about to be extinct before the asteroid hit?

It is common knowledge that dinosaurs were wiped off the planet when a mega asteroid crashed over the Yucatan Peninsula over 60 million years ago. Ever since, the hot topic of debate in every conference related to these terrestrial gods has been about the suspicion on whether the dinosaurs were already in decline before the asteroid destroyed them?

The surprising study

Well, a study published in Current Biology has attempted to settle the debate by advocating that the idea that dinosaurs were already declining before the asteroid struck, is based on faulty fossil data. "It's been a subject of debate for more than 30 years — were dinosaurs doomed and already on their way out before the asteroid hit?" study lead author Chris Dean, a paleontologist at University College London, said in a statement.

The study analysed nearly 18 million years of fossil evidence which included records of around 8,000 fossils from North America dating to the Campanian age (83.6 million to 72.1 million years ago) and Maastrichtian age (72.1 million to 66 million years ago). They focused on four families, namely, Ankylosauridae, Ceratopsidae, Hadrosauridae and Tyrannosauridae.

The revealing results

The dinosaur diversity peaked around 76 million years ago and then shrank until the asteroid wiped them out, revealed the analysis at face value. This decline was even more profound in the 6 million years before the mass extinction when the number of fossils from all four families decreased in the geological record. However, as per researchers there is no indication of environmental conditions or other factors leading to this decline.

Thus, it is possible that the Maastrichtian may have had poorer geological conditions for fossilization. As per researchers, geological events such as the retreat of the Western Interior Seaway which ran from the Gulf of Mexico to the Arctic and the rise of the Rocky mountains around 75 million years ago, may have disrupted the fossilization of these dinosaurs, making it appear as if they were less in number and diversity. Additionally, the team also found that geological outcrops from the Maastrichtian of North America were not accessible to the researchers.

The team found that the Ceratopsians, a group that includes horned dinosaurs like Triceratops, were the most common in fossil records as they inhabited the plains and thus their fossils were preserved. However, the Hadrosaurians, duck-billed dinosaurs were the least common as they lived near the rivers where the river flow may have receded the deposits of sediments that could have preserved these dinosaurs, the researchers wrote in the study.

"Dinosaurs were probably not inevitably doomed to extinction at the end of the Mesozoic [252 million to 66 million years ago]," study co-author Alfio Alessandro Chiarenza, a paleontologist at University College London, said in a statement. "If it weren't for that asteroid, they might still share this planet with mammals, lizards, and their surviving descendants: birds."