|Mysteries of the
By Chris Yukna
A great deal of the enigmas associated with the Age of the Dinosaurs has to do with gigantism. Everything seemed to be huge. So let's start off with some of those giants whose existence precedes the dinosaurs.
Members of the phylum Arthropoda:
Maybe science should have had a category called ThunderInsects because they were big. Take for example the centipede or millipede of today (okay not an insect). You lift up a rock or you look among the leaf litter and there might be a little creepy crawly of a few inches long. According to the book: "A Short History of Nearly Everything" by Bill Bryson , even before the dinosaurs, centipedes were often a meter long and some reached two meters in length. Another frightening example is giant sea scorpion from approximately 400 years ago. These scorpions seem to have been mansized or larger. They are oddly named as well, since giant sea scorpions usually described as living in swamps and rivers. Moreover, there have been reports of huge scorpion footprints in dry land... Today we don't have any land dwelling animals with exoskeletons that are any where near that size. One main reason is physical. Insects, spiders, centipedes and the like are limited in size because of the way they breathe. They generally don't have lungs like ours that expand and contract. Therefore supplying large bodies with enough oxygen becomes a real problem. In mammals, birds and reptiles the uptake of oxygen in the blood and the release of carbon dioxide from the blood takes place in the lungs. Then with system of veins and arteries the oxygen is pumped back and forth throughout the body by their hearts. Arthropods have many ingenious ways of diffusing the oxygen throughout their bodies Some insects, spiders, etc. have leaf-like structures, book "lungs", through which blood flows. There are also small tubes run from the exoskeleton into the body. If I remember correctly these are called trachea. There oxygen and CO2 are exchanged with the blood by diffusion. However, while there is a heart and there are vessels to transport blood to a specific location in the body, it is not a closed system. The blood simply fills all the empty spaces around the internal organs.
This system is not any where near as efficient (as size increases) as our circulatory and pulmonary system and therefore is probably one of the most important limiting factors in the size of land arthropods today.
Those Magnificent Flying Animals
Back to those pesky and inexplicable monstrous centipedes. With such huge arthropod predators running about it was no wonder that insects learned to fly. That is one of the mysteries of science: the origin of insect flight. It is really hard to figure out how one evolves a wing. I mean do you start out with a tiny useless wing and somehow enlarge it over time or begin jumping and wings sort of happen to aid you to land. Apparently it is extremely difficult to run a computer simulation that shows the evolution of the whole package: wings and the muscles and nerves etc. You can see the advantages of flying just not how you start out to evolve in that direction.
Speaking of flying insects like this dragon fly pictured below:
On to bigger flying objects: the dinosaurs themselves or as some people call them flying lizards:
Here we come again to problems of modeling these animal's flight. They were so big and had to be so heavy we can see how they could glide but taking off seems to present real problems. I suppose they could have lived on cliffs and jumped off them to fly but what on earth happened to the pterosaurs if they touched down. You can not miss the fact that the pterosaurs resemble seabirds. Form generally follows function. If these animals dined on fish as everybody thinks they did, then how did they get airborne after catching their prey? Compare today's waterbirds taking off on water as opposed to ground, it takes more energy. Plus fish and any water they gulped down would decidedly increase their payload. Curious, no? In his wonderful monogram: Was the Atmospheric Pressure Different at the Time of Dinosaurs? Octave Levenspiel goes into aerodynamic detail as to why these animals could not fly. He also describes quite well the quandary of how to get blood up to the head of a giant apatosaur. There seems no obvious solution except...more on that later.
Behemoths of that long ago time were not only limited to animals. Simple plants got their dose of growth formula too.
Another facet of the puzzle is that plants grew also much faster in the Cretaceous era.Which can be explained by..... dunno. More water, more carbon dioxide, and more oxygen have been suggested. One such researcher is Sara M. Decherd and you can read a press release on her work: A Lot of Hot Air: How the Dinosaurs Grew So Monstrous.
Polar Dinosaurs and Climatic Mystery
During the Mesozoic or "The "Age of Dinosaurs" first Australia then Antarctica occupied the South pole. This may be a little confusing since they were at one time attached with Australia breaking away and heading North. At any rate, what were these continents covered with? Tropical rain forests! Yes, that is very strange don't you think? Some people have explained away this fascinating enigma by saying that it is obvious that if there were tropical rain forests at the South Pole than the Earth was warmer. As much as six degrees Celsius has been suggested. Think about this: a night that lasts three months could be negated by increasing the overall temperature of the Earth. This is accomplished apparently without producing any drastic climate change at the equator. No evidence of increased desertification has been noticed in equatorial areas. Yet the the entire planet was supposedly much warmer and totally tropical. A good place to check out is David Esker's Mesozoic Paleoclimate. How on earth did heat from the equatorial zone get transfered to the poles? I would love to see some simulation of our planet explain how these forests and animals could have existed in the land of the midnight sun.
A lot has been written about Polar Dinosaurs too, giving them special adaptations to cold, night vision, maybe fur or feathers. Funny, do you think that those fossilized tropical plants somehow had antifreeze when they were growing on those two continents? I mean ginkos, ferns, cycads (palm-like plants), have been found at the poles during the Mesozoic. What is wrong with this picture? Well, we have already mentioned ferns as being fairly delicate, in fact the only really large versions are to be found in tropical rainforests. Ginkos are adaptable to lots of climates but the Ice Age nearly wiped them off the face of the Earth. As to cycads, well they are described as small element of the flora ecology in tropical and subtropical areas. You see why it seems odd to find them inside the Antarctic circle.
Where is the Tree line?
Another puzzle of this time is lack of Mountains or at least lack of any fossilized alpine flora and fauna. (Not that you can't find fossils in the Rockies and the Alps.) Everywhere you look appears to be tropical forests.
No one mentions any mountain ranges or fossils from high altitude plants and animals. This may be a problem of my lack of knowledge or that fossils from alpine areas would be exceedingly hard to find. I do remember reading that some one even theorized that there were no mountains in Pangaea .(obviously I have more research to do)
Increased Oxygen Levels Fuel the MegaFauna ?
Recently, all of these puzzling facts can be explained by the fact that there was more Oxygen in the atmosphere. Some scientists estimate that there was 35% oxygen level in the atmosphere at the time of the dinosaurs. You may want to read Dinosaur Breath by John G. Cramer This certainly would explain how arthropods could oxygenate their oversized bodies.
Fossil evidence for this increased Oxygen levels can be found in how fires burned back then and their fossilized traces. Fire burned very rapidly. Plus there seems to be air trapped in amber and the ratios of Oxygen 16 and 18 indicate that there was more oxygen available. This explains everything right? Remember those seagull sized dragonflies. Well some people tried to raise them in greenhouses with an atmosphere of 35% oxygen. The results were disappointing: some slight increase in size. To give them credit, perhaps with time the dragonflies could have evolved into giants. However, there still is a problem with these airborne dragonflies . If enriched Oxygen levels allow increased energy expenditure then there would be an augmentation of heat. Thus the flies would burn up. Dr.Michael May has worked on how these ancient insects might have dissipated heat differently than modern insects. This seems to be an interesting read Warming rates as a function of body size in periodic endotherms Covering insects up to mammals. Unfortunately I don't know where you can read the entire work. The problem associated with increased energy use applies to the pterosaurs as well.
One minor note of discord, some studies seem to indicate that high levels of oxygen can impede the growth of plants.
Increased Magnetic Field at the Time of the Dinosaurs.
When the dinosaurs walked the Earth, the planet's magnetic field was three times as strong as it is today. This is positively stupendous. Current theory demands that the Earth's core is the heart of its magnetic field. Why would the field drop so quickly to one third its value in so short a time: one hundred mllion years. There are many questions here. When did it drop or how long did it take, etc? How much an influence was the Earth's rotation? After all, the Moon is moving away from the Earth and this is making our days last longer.
An Alternative: The 2 or 3 Bar Theory
What if the atmosphere was considerablely denser? Instead of changing gas ratios you increase pressure by two or more bars. Scientists already agree that the atmosphere was not the same in the age of the dinosaurs.
You know, no one is sure why or how the Earth maintains a constant level of Oxygen at 21%.. Oh sure, plankton creates shells out of calcium carbonate and plants produce oxygen, etc. But the grand design for regulating the levels of gases in our atmosphere are not well understood. What would have altered those processes so much as to double the level of oxygen does not seem to be clear.
Let's suppose instead that the Earth's atmosphere in the Cretaceous was not one bar (or 1 atmosphere) at sea level but two or more. This is not too far fetched. Venus, Earth's sister planet has an atmosphere of 90 bars (or atmospheres) and has slightly less gravity than our planet. As for a planet losing an atmosphere over time, Mars seems to present a pretty good case . No need to call on Creationist flood theories. If we were a planetary scientists studying an unknown terrestrial planet orbiting an unfamilar star then the idea of a planet the size of Earth having an atmosphere of two or three bars would not be disturbing. (Having half that atmosphere disappear rapidly is another story.)
What does that do to the mysteries? It seems to solve all of them. At least those I know of.
Big Creepy Crawlies
Giant arthropods would be able to breathe easier through their exoskeletons. At two bars the diffusion of gasses throughout their breathing systems should be more efficient thus allowing for enhanced proportions. The increase in pressure might give their bodies more rigidity. Again, I would like to run a computer model on insect bodies living under extreme pressure. Water for example is a very strange liquid. It is uncompressable. How water filled structures react under high pressure would be meaningful.
One of the largest arthropods is the giant Japanese spider crab. Measuring 3.7 m from claw to claw in some cases. They live at deeps of 50 to 300 meters in the Pacific Ocean off Japan. Obviously something in this dense environment allows them reach such a size.
Flying Lizards and Insects
I'm not completely sure but by increasing atmospheric pressure I would assume that the effect or effects would be exponential. Computer modeling of flying lizards and monstrously sized insects becomes a whole lot easier. I wonder if there is already wind tunnel data on high pressure aerodynamics? The evolution of insect flight might be simplified or not. What I mean to say is that in a denser atmosphere fight would be a whole lot easier.
Again Octave Levenspiel has illustrated that point succinctly in the beginning of his article
I assume you know that the atmosphere is thicker at the equator than at the poles. Yes, the thickness or height of the troposphere varies by latitude. I would think that a denser atmosphere would mean a thicker one as well including at the poles. Therefore just running a simulation of atmosphere would probably demand changing quite a few parameters. I have not yet had a chance to model thermal transfer on a global scale but say an atmosphere at two or three bars would seem to be like using a pressure cooker: delivering a more even distribution of heat throughout the planet. This might explain tropical or semitropical temperatures at the poles. If heat was more efficiently distributed throughout the atmosphere then even the equatorial zone may have been more temperate in a global climate that would have been considerably warmer. Another aspect of a denser atmosphere that is hard to understand or forecast is the odd effects of water under increased pressure. For example, most liquids as you increase the pressure become solid, but water's freezing point decreases as pressure increases until you reach 1000 or so atmospheres. Most climatic simulations rely heavily on starting conditions. A few tenths of a degree this way or that, changes in winter snowfall levels, etc can vastly alter the outcome of these forecasts. One interesting point in the 2 or 3 bar Earth theory would be the effects on snowflake formation, snow precipitation, and snow melt. Another would be the effect on planets and freezing. If conditions are less favorable for the formation of ice crystals inside plants and animals, then a tropical forest at the south pole seems again more feasible. After all it is the expansion of these crystals that ruptures cell walls. However, the ratio of ice to liquid with water under pressure increases as the pressure augments, therefore when ice does form the damage should be more severe. Weathering of rock from water freezing and melting would also be accelerated and might just possibly leave a trace.
Now, let's touch on plant growth. If our atmosphere were doubled or at least greatly increased it might explain why plants grew much faster. Not only would there been more gases like oxygen and carbon dioxide but I would assume that denser atmosphere would support a greater humidity. More water vapor the more likely a worldwide tropical climate would have ensued. I mean everyone says that plants grow better in a hot house. Moreover, by augmenting atmospheric pressure the tree line would probably be at a much higher altitude. This might explain the lack of alpine environments in those eras.
Hot Fossil Fires
At higher pressures there would be more oxygen available and fires would be that much more intense as again fossil records show. How you ask? How much oxygen is available for a fire reminds me of the fire in Apollo 3 in January 1967. In the capsule NASA was using 100% oxygen at sea level. There was a horrifying blaze that killed the three members of the crew. To rectify the problem engineers greatly reduced cabin pressure after the accident. Thus eliminating the possibility of another such horrific inferno. So another line of research will be to see if there are differences in burn patterns under high oxygen ratios or high atmospheric levels. I wonder if there is any difference at all. For further reading you could start with
Further or Potential Research
A high rate of plant growth might easily be demonstrated with pressurized greenhouses. At present Francois Valdivieso and I plan to have our first year students examin the problem. They will have access to all the tools to build small boxes with various pressures and put identical plants inside. Although they may propose other methods of studying the problem. It is a rather unique approach to education. Usually, we give the specifications of the lab project and the students execute the work. This simple experiment is a promising beginning.
We could get more ambitious. Instead of Biosphere2 maybe we could build Cretaceous2. (Although, I can't help but picture in my mind the scene of giant vegetables from Woody Allen's film: Sleeper. Would an huge apple grown in a hyper pressurized greenhouse explode in your mouth or all over the supermarket?)
Another project for the "Son of Triassic Greenhouse" would involve insects. Flying insects would be intriguing to raise under a pressure of three atmospheres.Maybe it would be cheating but it would be interesting to tilt the environment to favor larger size. Killing the small ones for example. Of course a control greenhouse with the same conditions except at sea level would be mandatory .Amusing task to say the least. How long would it take to see significant results? A good rule of thumb would be 12 generations. That is the time it takes to transform a normal horse into a miniature breed with selective breeding. I am talking about a miniature horse and not a pony. Just how long are dragonfly generations?
At present we are looking to set up a sort of think tank to tackle this undertaking.
Increasing the atmosphere does appear to make things less mysterious. From insects to dinosaurs, plants to climates a great deal seems to be simpler.
So if we were to apply Occam's Razor (one should not increase, beyond what is necessary, the number of entities required to explain anything.) it seems logical that the atmosphere was much dense than today. We don't live in a logical universe. This thought exercise could be completely wrong. This endeavor is very multidisciplinary and a work in progress. I would hope that you the reader would like to help test the ideas mentioned here. Don't hesitate to contact me.
If the Earth did lose a significant portion of its atmosphere as little as 65 million years ago the implications are staggering.
First because sixty five million years ago in geological time is like yesterday or maybe this morning. Second, losing a major part of our atmosphere makes it less likely that in the event of another impact that life on the planet might be forever impaired.
Why or Where did it go?
What would have been the mechanism of this catastrophic change on Mother Earth? I could speculate. It may not have been instantaneous and then again it might have. But boy doesn't that sound like a lot of fun to research?
There are people looking at this as one possible candidate for the destruction of our atmosphere although they may not be aware of this aspect of their research:
An inferno in the atmosphere is what a team of scientists think happened after the asteroid struck the Earth off the coast of Mexico sixty five million years ago. Doug Robertson, the leader of team based in University of Colorado, thinks that the Earth was turned into a huge stove after the impact, killing most aboveground life in hours. (Now, I imagine that they based their figure on a one bar atmosphere, I do wonder what would happen if you changed this parameter) Other Modeling of the asteroid impact has shown that a significant portion of the atmosphere and dust was blown into space. If we add that to the loss of atmosphere to a sort of global firestorm? By the way, our planet does not lose helium gas because it is lighter than say nitrogen and simply floats away. No helium and for that matter hydrogen have less mass as atoms and thus thermally can easily reach escape velocity (hit by photons etc). If the atmosphere were superheated elements like oxygen and nitrogen could also reach escape velocity.
Speaking of firestorms you may want to read Did Asteroid-Induced Firestorm Destroy the Dinosaurs?
Or why not wander around this wonderful geological time machine?
If you liked this article you may find Canadian Fishing at the Grand Banks, Zebra Mussels,and Iron's Effect on Plankton an example of plausible connections by this author, intriguing as well
As always, we need more money to do more research.
Liliane Bois Simon as always for her help at editing
Octave Levenspiel for his kind advice and encouragement
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