New research from University College London challenges the notion that dinosaurs were already in decline before the asteroid impact 66 million years ago, suggesting that gaps in the fossil record may have skewed our understanding of their extinction.
Key Points at a Glance
- Study analyzed over 8,000 dinosaur fossils from North America dating between 84 and 66 million years ago.
- Apparent decline in dinosaur diversity may be due to fewer accessible rock formations from the late Cretaceous period.
- Occupancy modeling indicates stable dinosaur habitats leading up to the asteroid impact.
- Detection probability of fossils decreased over time, affecting perceived species diversity.
- Findings suggest dinosaurs may have been thriving until the sudden extinction event.
For decades, scientists have debated whether dinosaurs were already on the path to extinction before the catastrophic asteroid impact that marked the end of the Cretaceous period. A recent study led by researchers at University College London (UCL) offers a fresh perspective, indicating that the perceived decline in dinosaur diversity may be more reflective of fossil record limitations than an actual decrease in species.
The research team scrutinized over 8,000 dinosaur fossils from North America, spanning the 18 million years leading up to the asteroid impact. At first glance, the data suggested a peak in dinosaur diversity around 75 million years ago, followed by a decline. However, the researchers identified a critical factor: the quality and accessibility of fossil-bearing rock formations from the later Cretaceous period were significantly reduced, leading to fewer fossil discoveries from that time.
To address this, the team employed occupancy modeling, a technique commonly used in ecology to estimate species distribution while accounting for detection biases. By dividing North America into a grid and analyzing geological and environmental data, they assessed the likelihood of various dinosaur clades—such as Ankylosauridae, Ceratopsidae, Hadrosauridae, and Tyrannosauridae—inhabiting different regions over time.
The results revealed that the potential habitats for these dinosaur groups remained relatively stable throughout the late Cretaceous. However, the probability of detecting their fossils decreased, primarily due to the diminishing exposure of relevant rock formations and other environmental factors that hinder fossil preservation and discovery.
Interestingly, the study noted an exception with Ceratopsian dinosaurs, like Triceratops, which appeared more frequently in later fossil records. This anomaly is attributed to their preference for floodplain environments, which were more conducive to fossilization and have remained more accessible to paleontologists.
These findings suggest that the narrative of a gradual dinosaur decline may be an artifact of an incomplete fossil record rather than a reflection of actual biodiversity loss. The study underscores the importance of considering geological and sampling biases when interpreting paleontological data.
By highlighting the limitations of the fossil record, this research invites a reevaluation of long-held assumptions about dinosaur extinction. It emphasizes the need for cautious interpretation of paleobiological trends and supports the view that dinosaurs were likely thriving until the abrupt environmental upheaval caused by the asteroid impact.
Source: University College London
