The dinosaurs' extinction.

  As for the extinction of the dinosaurs the only solid fact is that no trace of dinosaur has been found after the Cretaceous. This calls for ideas of their sudden disappearence, and a great numbers of theories have been proposed, many of which with a preference for the dramatic.
  It should be emphasize, however, that their is no reason to think that the dinosaurs disappeared suddenly. And there is neither any reason to think that they disappeared because they all died! All animals die, but extinction happens because lesser new are born than die.
  The dinosaurs were a very great succes and the superiors of their time with no competition from other vertebrates. The mammals, which did exist during the entire dinosaurian period, were small nocturnal animals which played only little or no role to the dinosaurs.
  At the beginning of the Triassic various other groups of reptiles, which had survived the great extinction, took their place in the ecological system of the Mesozoic. Those were the diapside reptiles which evolved into the quadrupedal, sprawling lizards, and the herbivore rhynchosaurs, but the former stayed small, and the latter were slow, clumsy animals which died out during the Mesozoic. The birds arose during the rign of the dinosaurs, and also did the flying reptiles, the pterosaurs, but non of these met the dinosaurs with any kind of competition, neither did the amphibian archosaurs, phytosaurs and crocodiles, and nor the various species of sea-living reptiles, the ichthyosaurs and the plesiosaurs. From the Middle Triassic the stage was entirely set for the dinosaurs, and they constituted almost exclusively an eco-system of their own.
  This system was based on the tall plante-eaters, the sauropods, the various ornitischians, and eventually on the bird-like, plante-eating ornithomimians. These plant-eaters drifted in hosts over the landscapes and consumated enormeous amounts of plants, which they transformated into enormeous amounts of meat.
  These hosts of plante-eaters were escorted by the meat-eaters, the tall carnosaurs and the lesser bird-like coelurosaurs which profitated from the vast amounts of meat to be served when a tall plante-eater died, fell ill, or was wounded. Occasionally they might have attached and killed a prey, presumably young or invalid ones which could be overtaken, but there is no reason to imagine the meat-eating dinosaurs as active, chasing predators. More likely they should be imagined as scavengers, equipped with large teeth and sharp claws for cutting through thick and tough hide and for carving the meat, rather than for killing a living prey.
  The dinosaurs owed their superiority to the narrow gait which they had achieved from the swimming and bipedal ancestrial archosaurs.
  This gait made them able to evolve long legs and to move in a manner which demands much lesser energy than the original sprawling gait and the semi-improved gait of the pre-mammals. Besides it made them able to acquire large size.
  Due to this superiority the dinosaurs in general did not need to evolve neither essential physiological improvements nor essential improvements of senses and breeding as did the contemporary mammals. Some dinosaurian species might have improved their digestion and have developed a higher metabolic rate with some degree of endothermy, and some might have attained some kind of youth-care. And it is the most likely the bird-like coelurosaurs of Late Jurassic and Cretaceous, defectors from the bird-lineage, were warm-blooded and had a rather high metabolism as well as an advanced activity. But in general the dinosaurs remained reptiles with low metabolism and low activity-level, and with humble ability to orientate.Their ability to recognize objects of their surroundings were surely poor and confined to eye-sight, and only to a very small degree to hearing. The ornamental crests in the late ornithopods may have given these some ability to orientate by smelling, but there is in general no reason to think of the dinosaurs as particular active and agile, not to say intelligent, and no more than any modern reptile or bird.
  During the Mesozoic the dinosaurs evolved into a great number of species, each adapted to its niche, and by the end of Cretaceous the entire dinosaurian world was one great, complicated, delicate ecosystem.
  Their generally tall size, compared to other animals of their time, and their long legs confined the dinosaurs to the open, flat, and firm lands, and - like the modern tall, long-legged plain-living mammals - unsuited for rocks, swamps, and dense forrests. During the greater part of Mesozoic the latter was, however, no disadvantage as the herds of plant-eating dinosaurs on their all-consumating wanderings over the landscapes bit down all green plants and prevented any dense, tall vegetation to grow.
  The dinosaurian world was based on the herds of tall plant-eaters which lived mostly on ferns and conifers, which trees cannot stand to have the green parts bitten off. So when a host of dinosaurs had passed, the ground was left with bare, dying, and crushed trunks and heaps of dungs. Then new plants could grow up until the next herd of plant-eating dinosaurs came along, followed by their meat-eating compagnions.
  But in the Cretaceous the foliage plants and the foliage trees evolved. These plants could stand to have the green leaves bitten off; they grew new foliage and grew on. Thus great areas eventually became forrest, and the space for the dinosaurs was gradually reduced.
  The dinosaurs did not die from this, but the balance of the ecosystem was upset, and the number of plant-eaters decreased, slowly at the beginning, faster later on as the forrests extended. This further minimized the space for the dinosaurs which decreesed, and so on to an increasing degree. By the end of Cretaceous the entire eco-system collapsed. Due to their specialization as plain-dwellers with restricted physiology and sences the dinosaurs were unable to adapt themselves to the new situation. In a realtively short time they disappeared, leaving the earth to be covered with forrest.
  This had its consequenses: The amount of carbon-dioxide, CO2, in the atmosphere is lesser than 1 %, but the plants live on it and tie it as cellulose, thereby removing it from the atmosphere. But as the herds of dinosaurs eat almost any plant, the tied CO2 was released to the atmosphere all the time. But when the forrests began to spread, the great amounts of tied CO2 were no more released, and the CO2-amount of the atmosphere decreased.
  In the sea, the algeas also depended on the CO2. During Cretaceous enormeous amounts of CO2 were consumated by the algeas which tied it and diposed it as chalk. But as the increasing forrests tied still larger amounts of CO2 and the atmospheric amount of CO2 fell, the algeas of the sea decreased which upset the ecological balance of the sea too: The algeas were food for other sea-organisms, which were food for fishs and other see-animals, which also decreased, why the lope-finned fishs and the see-reptiles, ichthyosaurs, plesiosaurs, mesosaurs ect. consequently disappeared.
  These factors, and surely many others, brought the world of the dinosaurs to an end, leaving a world covered with foliaged forrests, and the possibility for the small, warm-blooded mammals to evolve.

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*)As most readers with interest for the subject are supposed to be familiar with relevant evidences, this essay deliberately is not garnished with numerous references.
  Only for the proposal of the pro-avian lineage should be refered the author's small book, Palm, Svend, (1997) The Origin of Flapping Flight in Birds. Ballerup. (ISBN 87 - 986364 - 0 - 5). As for the question of dinosaurs warm-bloodedness is refered to Palm, Svend, (1997) The Warm-blooded Dinosaurs? Ballerup. (ISBN 87 - 986710 - 0 - 6). Each can be required by E-mail: palm@post7,

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Attached: Illustrations, fig. 1 - 4 and 5.