• Scientific classification: Cephalopoda (class), Ammonoidea (subclass)
  • Epoch: Devonian to Cretaceous (419 to 65 mya)
  • Conservation status: Extinct
  • Cause of extinction: K-Pg asteroid impact
  • Fun fact: Closest modern relative is the pearly nautilus

Additional sources: Britannica, Wikipedia

Image source: Fossilera

Darwin says extinctions are gradual, but the Great Auk showed that man can really alter the normal pace of extinction. But as it turns out, Cuvier wasn’t all that far off. Walter Alvarez, with the help of his father Luis, was the first to find evidence of and propose a massive asteroid strike as the cause of the Cretaceous-Paleogene extinction. The Alvarezes were ridiculed by the scientific community until an appropriately large crater was found in Chicxulub, Mexico and the surrounding waters of the Gulf of Mexico. So why does Kolbert choose to feature the Ammonites?

The Ammonites were an extremely diverse group of creatures for millions of years. They were by all means an evolutionarily successful animal. Specifically, this success for them looked like laying minuscule eggs and producing hatchlings that had no means of moving about and as a result were confined to the surface of the water column, living in anonymity as plankton as they develop. This is unlike their extant cousin, the nautilus, who lays much larger eggs and whose hatchlings are mature enough to begin hunting for food in the depths. When a meteor strikes, you do not want to be at the surface of the water. And so the ammonites, who from an evolutionary standpoint had done nothing wrong, were completely obliterated. And this is what Kolbert seeks to emphasize: that outside forces (such as mankind) can completely rewrite the rules of the game of evolution.

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