Now listen to part of a lecture on the topic you just read about. We know the Ammonite extinction happened, but none of the theories trying to explain the details of how it happened is convincing. Here's why. First, it's unlikely that the rainfall that followed the impact was acidic enough to kill off the Ammonite young. You see, if the rain falling on Earth after the impact had been extremely acidic, it would have severely harmed other organisms, like frogs. Frogs and related organisms live much of their lives in water, and are particularly vulnerable to acidic waters, but frogs and similar water dwelling organisms, which probably would have been killed off by months of harsh acid rain, did not go extinct 65 million years ago. If the rainfall did not kill off these organisms, it's unlikely it killed off the Ammonites. Second we cannot really conclude that all, or even most, ammonites were dependent on zooplankton as a food source. The ammonite fossils with special Jaws you read about belong to only one group of Ammonites. There's no fossil evidence that the many other ammonite groups had these jaws for eating zooplankton, we cannot draw the conclusion that all the Ammonites ate zooplankton based on fossil evidence about just one group, so we can't conclude that the zooplankton die off drove all the Ammonites to extinction. Third ammonites as a group may have actually been able to tolerate low oxygen levels pretty well. You see fossil evidence suggests to us that ammonites had very efficient organs for breathing. These efficient breathing organs functioned well even in environments with a limited supply of oxygen because of their efficient breathing organs and their seeming ability to survive in low oxygen conditions, a lack of oxygen does not seem like a very convincing reason for their extinction in.