66.5 million years ago
This April 6 on Logarithmic History marks the most famous mass extinction ever, the one that did in the dinosaurs (okay, okay, the non-avian dinosaurs).
Just a few years back, we had news of one of the most extraordinary fossil discoveries ever, in North Dakota: a graveyard of fish piled on one another by a tsunami-like wave, and mixed with burned trees, and the remains of mammals, mososaurs, ammonites, and insects, and a partial triceratops, formed within hours of the asteroid impact that wiped out most life on Earth. Here is a news release, 66 million-year-old deathbed linked to dinosaur-killing meteor, and here is an article from the New Yorker, The Day the Dinosaurs Died.
The end-Cretaceous extinction isn’t the biggest ever, but it’s the one everybody knows about. The Disney movie Fantasia (1940) did a version of the event, set to Stravinsky (and mixing up Jurassic and Cretaceous dinosaurs). In Terence Malik’s movie The Tree of Life, a predatory dinosaur discovers compassion in an encounter with a hadrosaur just before all their kind are wiped out by an asteroid: mass extinction meets the Book of Job.
The discovery that dinosaurs (and about 70% of all species in total) probably went extinct as a result of an extraterrestrial impact did more than anything else to bolster catastrophism. For most of the history of modern geology, geologists have mostly argued instead for uniformitarianism: the same slow processes we see today caused past geological and evolutionary changes. When evidence for an impact was first discovered – a thin layer of iridium, presumably extraterrestrial — paleontologists were pretty uniformly hostile: no physicist was going to tell them how to do science. But by now the evidence is overwhelming that the asteroid impact that left the Chixculub crater, in what is now the Yucatan, was largely responsible for the end-Cretaceous extinctions (although the volcanic eruptions that created the Deccan traps in India may also have played a role).
But at the same time that evidence has increasingly vindicated the catastrophist position, new discoveries in paleontology have increasingly brought home that one group of dinosaurs survived the extinction. Most people think of birds and dinosaurs as two quite distinct kinds of animal. But birds are just as much dinosaurs as bats are mammals. Many dinosaurs had many of the distinctive features of birds – warm-bloodedness and high metabolic rates (probably), wishbones, an advanced respiratory system, feathers (sometimes brightly colored, sometimes used for courtship), and parental care for nests of eggs and juveniles. It’s even possible that some flightless dinosaurs, like the turkey-sized Caudipteryx, were secondarily flightless, descended from flying ancestors like Archeopteryx. We don’t have to hope for The Lost World or Jurassic Parkto come true to see living dinosaurs; a trip to the park, with The Sibley Guide to Birds (or appropriate guidebook for your region) in hand, will do it.