Slate examines the mysteries of the mass extinction that killed all the dinosaurs… except the birds:
“Dinosaurs were killed by an asteroid 65 million years ago” is now an indicator of outdated understanding. For one thing, geologists have recalibrated the end of the Cretaceous Period (the final stage of the Mesozoic Era) to 66 million years ago. Granted, from the perspective of deep geologic time, a million years might not seem like much, but given that this was a world-changing event, we might as well get the date right.
More importantly, though, the Dinosauria didn’t totally expire in the catastrophe. Birds are a surviving lineage of dinosaur.…
Mammals were not locked into a standard body form. They were a diverse bunch, and much like the dinosaurs, they were hit hard by the mass extinction.
…
Had things turned out differently and the marsupial lineages continued to dominate, history would have taken a drastically different shape. Perhaps, in such an alternate universe, a marsupial-run Slate would offer articles like “Carrying Your Joey in Your Pouch: You’re Doing It Wrong.”
…
If the iridium band among the ammonite fossils is in place, Neil Landman and colleagues propose, then the mass-burial layer may represent ammonites that underwent a brief population boom in the aftermath of the impact, only to die off hundreds or thousands of years later when marine productivity collapsed.
The authors are tentative about this conclusion, but the notion that some extinct lineages survived for centuries after impact is not far-fetched. The concept fits with a phenomenon called the Signor-Lipps Effect, which holds that due to the incomplete nature of the fossil record, we will probably never find the last member of a species.
When a system unravels, it does so slowly. An ecosystem twitches as it dies….