TEMPO.CO, Jakarta – A period of global cooling caused a sharp decline in the number of dinosaur species about 10 million years before the extinction event caused by asteroid, according to a June study.
Studi yang dipublikasikan di Nature Communications itu adalah produk dari kolaborasi internasional yang menampilkan ahli paleontologi dari Université de Montpellier di Prancis, Universitas Bristol di Inggris, dan Universitas Alberta di Kanada.
Sekitar 66 juta tahun yang lalu, asteroid selebar 12 kilometer menabrak semenanjung Yucatán di Meksiko, memulai musim dingin nuklir yang menyebabkan kepunahan dinosaurus.
Tim peneliti berfokus pada enam keluarga dinosaurus, tiga karnivora dan tiga herbivora, yang bertahan 40 juta tahun evolusi hingga asteroid menghantam Bumi. Mereka memeriksa fosil dari lebih dari 1.600 dinosaurus individu dari sekitar 250 spesies yang berbeda secara total.
The results show that the biodiversity of the six families was already in sharp decline, some 10 million years before the asteroid hit. The study’s findings are significant, as declines in dinosaur biodiversity can be seen worldwide, in both herbivorous and carnivorous species.
Interestingly, one family that showed only a slight decline in biodiversity before the asteroid was the Troodontidae, a family of bird-like dinosaurs. Birds are known to have an evolutionary relationship with dinosaurs.
The researchers noted that herbivorous dinosaurs declined slightly before carnivores, so it is highly likely that the decline of herbivorous species directly led to the decline of carnivorous species.
This is an example of a cascade effect, where an extinction is triggered by the previous extinction of a different species in an ecosystem.
One theory why dinosaur numbers declined before the extinction event was climate change. During the Cretaceous period, between 145.5 and 65.5 million years ago, Earth experienced a global cooling period of 7-8 C.
Dinosaurs, which were mesothermic animals (needing a warm climate to maintain their body temperature and metabolic functions), must have been greatly affected by this period of global cooling.
New information about dinosaurs, as well as fossils, is discovered every day. In June, scientists discovered a new species in Australia.
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