The main problem with the environmental theory of dinosaur and other life form extinctions lies in the conflicting evidence in the fossil record. For example, evidence for the environmental theory includes ammonite (hard-shelled relatives of squid) fossil records. One record shows they were in decline for approximately 11 million years before finally going extinct, but other fossil evidence indicates the impact at Chicxulub suddenly killed off from one-half to three-quarters of ammonite species along the coasts of France and Spain.

Unfortunately, the fossil record of Cretaceous dinosaurs is very limited for the last 10 million years of that period. In fact, the only good dinosaur records from this time are in western North America—and this evidence is limited to the last two million years of the Cretaceous period. Thus, this poor, discontinuous dinosaur fossil record may be the real cause for the apparent reduction in their diversity, and not environmental causes.