In earlier research last month, it was shown how the extreme volcanism in the Deccan Trap was not responsible for the extinction. Hence, the other theory of asteroid hitting the planet that led to the ancient animal’s extinction seems more plausible. It was apparently this asteroid that hit the planet, giving birth to the Amazon rainforest in South America, says a new study. The paper titled Extinction at the end-Cretaceous and the origin of modern Neotropical rainforests, published in the Science journal this month, suggests that the origin of modern rainforests can be traced to the aftermath of the bolide impact after the Cretaceous. Researchers used fossilised pollen and leaves from Colombia to study how the impact changed South American tropical forests. The incident scientists refer to occurred when the 12km-wide asteroid struck Earth 66 million years ago. This incident drastically changed the vegetation that made up these forests.
Co-author of the study, Dr Mónica Carvalhofrom the Smithsonian Tropical Research Institution in Panama, used fossilized pollen and leaves to characterize the changes that took place in northern South American forests at this time. Their observation showed that not only were there changes in species composition, but they were also able to infer changes in forest structure. Examining over 50,000 fossil pollen records and more than 6,000 leaf fossils from before and after the impact, the team of scientists found that cone-bearing plants called conifers and ferns were quite common before the massive asteroid struck the region that is now the Yucatan Peninsula in Mexico.
The study finds widespread extinctions of plant diversity after the asteroid left its devastating impact, especially among gymnosperms. A new form of plant species took birth after the asteroid impact and researchers say it was Angiosperm taxa that came to dominate the forests over the 6 million years of the recovery period when the vegetation began to resemble that of modern lowland neotropical forest. The leaf data also indicates that the forest canopy evolved from relatively open to closed and layered that led to increased vertical stratification and a larger diversity of plant growth forms.