Chicxulub impact crater/ NASA, JPL
Sixty-six million years ago, an asteroid hit the Yucatan Peninsula in Mexico and produced cataclysmic disruptions that, it is believed, killed off about 75% of species (the K/Pg extinction). But many researchers think there must have been other factors at work. For example,
Fish, turtles, amphibians and crocodylians all generally fared better than strictly terrestrial organisms. “People have been observing this pattern since at least the 50s, and probably before,” Holroyd says. But the resilience of waterbound species had never been quantified in detail before, and the new analysis is revealing that the solution to the extinction pattern puzzle may have been right in front of us all along.
The surprise, Holroyd found, was that the difference between the survivors and the extinct of the K/Pg event mimicked a pattern that has held true for tens of millions of years before and after the asteroid impact. Species living on land, particularly large species, tend not to persist as long as those living in freshwater environments. Terrestrial species often go extinct at a greater rate than those in aquatic environments even without a massive catastrophe to take them out of the picture. Species that lived in and around freshwater habitats appear to have persisted longer even when there wasn’t a crisis, and when the extinction at the end of the Cretaceous struck in full force, these organisms had an advantage over their purely terrestrial neighbours. Brian Switek, “We Still Don’t Know Why the Reign of the Dinosaurs Ended” at Smithsonian Magazine
Pat Holroyd hopes that as more pieces of the puzzle are filled in, we will learn more about why aquatic life forms are at less risk of extinction.
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See also: The Atlantic: “Nastiest feud in science” erupts over dinosaur extinction theory
See also: 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.
Extinction: Had the dinosaurs been dying out before the big K-T extinction?
Dino diminuendo (They were dying out before the asteroid hit.) That might help account for why all dinosaurs disappeared but only a large proportion of other vertebrates.
Smoking did not kill the dinosaurs, but dark matter might have contributed
Dinosaurs doomed by egg-laying?
Size helped largest dinos survive longer?
Do mass extinctions happen every 26 million years or so?
Study: Two years’ darkness provides clue to total dinosaur extinction
and
We can’t understand evolution without understanding stasis and extinction