The Fates of Vertebrates Across the K/T Boundary
Without question there are more theories of how dinosaurs became extinct than for any other creatures that have inhabited this planet. In the late 1980s Alan Charig, curator emeritus of the British Museum of Natural History, informed me that he had tallied over eighty theories of how dinosaurs had met their demise. As I will argue in the closing chapter, it was probably not a single cause that brought the dinosaur extinction, but eighty causes surely is overkill!
I will not dwell on those theories for which physical or biological evidence is lacking, but will go directly to the three that have been most recently tested and debated. These are the impact theory, the volcanism theory, and the marine regression theory. I regard all of these as ultimate, not proximate. By this I mean that none of these events would have directly caused the extinctions. Rather each would have precipitated ancillary or corollary consequences that then did the deed.
This distinction is important. Moreover, it may be time for the debaters to join forces. Although doubters as to an impact, or volcanism, or marine regression near or at the K/T boundary remain in force, evidence is becoming overwhelming that all three occurred. In chapters 7 and 8 I will spend some time discussing these three events, especially magnitude and timing, but I accept them all as having been adequately demonstrated. What most requires testing, in my view, is