OK so what do you think as this as a possible explanation of why the larger animals died…
I guess its time to revise my claim regarding any gravity changes, but i still remember this idea discussed at length in class many years ago. I did find this offered as a better appreciation of what may have happened:
reprinted from this site-
[/http://www.equalparenting-bc.ca/members/planet_earth.htm
Why Were The Animals and Plants Larger During The Jurassic Age?
Fossil records indicate that the animals and plants, throughout the world, grew to record sizes for a period of time on this earth. This worldwide discovery of enlarged species cannot all be explained by genetic factors. Scientists, led by Dr. Carl Baugh Ph.D. from Glen Rose, Texas, researched the fossil records of plants, animals, and birds. They came to the conclusion that the Jurassic atmospheric had to contain more oxygen and more carbon dioxide with higher pressure than the present atmosphere (14.7psi.). Addition research at the University of Tokyo with tomato plants indicated that the higher pressure with more carbon dioxide stimulated growth factors in plants. Dr. Carl Baugh developed an academic model of this pre-flood Jurassic atmosphere. He believes that the atmospheric pressure was about 28psi absolute. His academic model calls for about 23% oxygen and ten times more carbon dioxide (3/10 of 1%). His research group has built the world’s first hyperbaric biosphere.
Fascinated with these discoveries, in the early 90’s I began studies into plant growth processes. This led to my personal discovery of plant enzyme functions and pH modifiers. By the mid 90’s I had built a research greenhouse to experiment with the Jurassic plant growth hypothesizes. Meanwhile, research in the Glen Rose hyperbaric biosphere continued to produce some amazing discoveries with snakes and insects. I also came across hyperbaric oxygen research in Russia that claimed some exciting healing benefits from high-pressure chambers with pure oxygen. In 1995 I turned most of my efforts towards developing a hyperbaric oxygen chamber for people, which would be based upon this Jurassic academic atmospheric model. My chamber was designed to operate at 28 psi absolute range (13 psi gauge pressure). I used air/oxygen concentrators to produce medical grade oxygen for breathing through nasal cannulas. This new design criteria and improved mechanical features proved to be lower cost to build and operate. Doctors began sending people to my research chamber to see what effects pressurized, oxygen-enriched air had on them. Although my research and results were not extensive, I was impressed with the safety and potential use of low-pressure air mixed hyperbaric oxygen chambers.
The conventional hyperbaric oxygen chambers use much higher pressures with 100% pure oxygen to treat a wide range of medical conditions. There is over 40 years worth of worldwide research in this field and in many cases the results are very good but limited. The high-pressure use of 100% pure oxygen increased oxygen toxicity and reduced the treatment times. Even so, the conventional chambers demonstrated accelerated growth and repair processes while improving the immune system’s functions. The biggest reason for the lack of available chambers has been the high cost to buy and operate these chambers.
Finally back to the point of this brief, why were the animals and plants so large? Scientists and medical researchers have found that the enzymes, in both animals and people, build and repair their own cells, tissue, and organ parts. Plants also have enzymes involved in the repair and building processes. Enzymes are called into action by growth and repair hormones. The past hyperbaric oxygen research has demonstrated the fact that the cell and tissue regeneration speeds up while at higher oxygen and pressure. I concluded that the enzymes are moving faster during those growth or repair hormone periods. I assumed that more available oxygen allows the enzymes to work faster. This would help explain why the animals and plants grew larger during the Jurassic age. Plants also rely on carbon dioxide (CO2) for their growth processes. The Jurassic studies indicated ten times as much CO2 at almost double the atmospheric pressure. The plants would have also absorbed more carbon dioxide, which through photosynthesis produced more sugar solution for the roots, thus stimulating faster plant growth. I think this research has potential long-term benefits for mankind. I hope more scientists get involved with the necessary funding to carry on.