Why did Sharks survive KT extinctions and not Ammonites?

Question

Nobody knows the answer to this, but it is worth seeing what others think.

Ammonites were the totally wiped out by whatever caused the extinction of the dinosaurs. Ammonites were those round, spiral shelled molluscs that prior to the extinctions swarmed in the oceans by the billions. There are fossils of them an inch across, and others 4 feet across. They were incredibly successful, and the hundreds of different species existed for hundreds of millions of years.

But they all disappeared 65 million years ago when the dinosaurs went. Not one is left. Not even a descendant. At least they think the dinosaurs gave rise to birds.

Then if the event, whatever it was, could kill off all these fairly small sea creatures, how come huge sharks survived in the same oceans? Lots of other shellfish survived. Why were these ones wiped out?

In its way, it is a much bigger mystery than the dinosaurs. It is just that we find dinosaurs much more exciting creatures.

Answer 1

Good question. When you look at any mass extinction event, there appears to be no logic. If you can, try to get hold of a book by Stephen J Gould called "Wonderful life" first published in 1989.

It actually concerns the Cambrian explosion, but he discusses "contingency" in survival a lot.

Incidentally, and another thing he talks about, it will not be adaptation as such. The sharks already had some advantage. It wasn't planned in any way, just luck.

Answer 2

Current evolutionary theory treats survival after a mass extinction event as, essentially, luck. Certain species may have traits evolved for other reasons that enable them to survive (such as feeding on carrion, or being able to hibernate for an extended period), but no species can "adapt" to an event that happens so rarely (only five major ones in 600 million years). Probably many species of sharks did go extinct 65 million years ago; if only one or two species survived, they could easily have given rise to all the modern species in a (relatively) short period of time.

Answer 3

Well I believe that ancient sharks adapt to the life near after the KT event while these ammonites probably were not able to survive. It is like Survival of the Fittest.

Answer 4

Adaptation