A new study has revealed that dinosaurs were not in a state of decline prior to the asteroid strike; rather, poor fossilization conditions and unexposed late Cretaceous rock layers imply that their remains are either not preserved or difficult to locate.
Fossil discoveries have long indicated that dinosaur numbers and diversity were decreasing before the asteroid impact at the end of the Cretaceous period, as reported by Live Science.
Some researchers previously hypothesized that this decline was evidence that dinosaurs were already on a path toward extinction even before the catastrophic collision with a space rock. However, this idea has been a subject of long-standing debate, with other researchers contending that dinosaur diversity was thriving at the time of their demise.
New research, published on Tuesday in the journal Current Biology, suggests that the apparent scarcity of dinosaur fossils before their extinction may simply be attributable to an inadequate fossil record.
The scientists examined records of approximately 8,000 fossils from North America dating back to the Campanian age (83.6 million to 72.1 million years ago) and the Maastrichtian age (72.1 million to 66 million years ago). Their focus was on four families: the Ankylosauridae, Ceratopsidae, Hadrosauridae, and Tyrannosauridae.
Their initial analysis indicated that dinosaur diversity reached its peak around 76 million years ago, subsequently declining until the asteroid impact that wiped out the non-avian dinosaurs. This trend of decreasing fossil numbers across all four families in the geological record was even more pronounced in the 6 million years leading up to the mass extinction event.
However, the researchers concluded that there is no evidence of environmental conditions or other factors that would account for this apparent decline.
