In previous posts on this blog and in postings to newsgroups, I have described my theory on how the dinosaurs died. Recent news articles have continued to support my ideas, and have suggested a mechanism for the great change that resulted in the extinction of the dinosaurs.
My "Last Gasp Theory" states that dinosaurs evolved to exploit a metabolic mutation that gave them an advantage in a thicker atmosphere with a higher concentration of oxygen. During roughly the same period, mammals evolved in high altitude locations (mountains) that had cold temperatures and thinnner atmosphere.
Suddenly, 65 million years ago, the atmosphere changed, reducing the amount of oxygen. The dinosaurs' metabolic advantage became a liability, and the mammals' adaptation to lower oxygen levels suited them to world-wide conditions rather than a limited environmental niche.
We now know that oxygen levels were higher at the time the dinosaurs were present. One of the questions created by my theory, is where did that oxygen go? Recent news articles have stated that ocean levels were far lower before the dinosaur extinction. Water is H2O, and of course the greatest mass of water is the oxygen. In order for large amounts of oxygen to become bound up as water, you have to burn hydrogen or compounds containing hydrogen, such as hydrocarbons.
If the major source of hydrocarbons is abiotic (from processes within the Earth, rather than 'fossil fuels') then there may be large amounts of hydrocarbons trapped under the crust of the Earth. This abiotic theory has been gaining ground since it was first proposed in Russian in the 1950s.
Assuming that there was a meteor or asteroid strke 65 million years ago, it may have 'cracked the crust' and released large amounts of hydrocarbons or hydrogen gas, which then burned, taking large amounts of oxygen from the atmosphere, creating water which raised the sea level. At the same time, the suddenly oxygen-poor air (by the standards of the dinosaurs) would become inhospitable to dinosaurs that lived both on land and in the water.
Another recent article states that mammals were more developed in their uniqueness earlier than was previously thought. The mammalian traits of hair, live birth, and suckling of the young all suggest adaptations to a colder climate, and if the atmostphere was thicker, that climate would have likely been at higher altitudes (or perhaps a combination of high lattitudes and higher altitudes).