Along with massive but not total extinction of many other life forms. From Laura Geggel at LiveScience:
The 2 minutes of darkness caused by the total solar eclipse earlier this week may seem momentous, but it’s nothing compared with the prolonged darkness that followed the dinosaur-killing asteroid that collided with Earth about 65.5 million years ago, a new study finds.
When the 6-mile-wide (10 kilometers) asteroid struck, Earth plunged into a darkness that lasted nearly two years, the researchers said.
This darkness was caused, in part, by tremendous amounts of soot that came from wildfires worldwide. Without sunlight, Earth’s plants couldn’t photosynthesize, and the planet drastically cooled. These two key factors likely toppled global food chains and contributed to the mass extinction at the end of the dinosaur age, known as the Mesozoic, according to the study.
The finding may help scientists understand why more than 75 percent of all species, including the non-avian dinosaurs, such as Tyrannosaurus rex, and large marine reptiles, such as the plesiosaur, went extinct after the asteroid slammed into what is now Mexico’s Yucatán Peninsula, the researchers said. More.
Let’s hope this finding is supported in future because it sounds highly plausible and may shed some light. We want to know why all dinosaurs and plesiosaurs went extinct, not simply why masses of individuals suddenly died. Something truly catastrophic must have happened.
In the past, the field has been littered with speculations such as that dinosaurs were dumber than mammals and did not look after their young. But we now know that some dinosaurs did look after their young and that the capacity to do so is much older than formerly thought. Also that placental mammals are not uniformly smarter than all other life forms.
Most extinctions seem to be fairly slow (background extinctions) and sometimes we are mistaken in thinking they have occurred.
See also: Did prehistoric reptiles look after their young?
Animal parenting at 508 million years ago
Does intelligence depend on a specific type of brain?
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Lazarus species: animals listed as extinct that turned up again.