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[A] first appeared on earth one birds. Size as a crow, feathers cover the body, have long hind legs and tail vertebrae. Triangular snout, the mouth has teeth, the front edge of the retaining wings claws, can obviously see that the form of reptiles. Bone structure from the point of view and small carnivorous dinosaurs are very similar. So some people think that birds are descendants of dinosaurs. Whether this argument is justified, but one thing is certain, that before the end of the age of dinosaurs, have a good variety of birds appeared. 1861, the German province of Bavaria, the Upper Jurassic Solnhofen limestone (ie, the formation of late Jurassic limestone formations) were found in one's most ancient bird fossils, not only to preserve bone, but also traces of feathers It was named Archaeopteryx. Since then, has a total of seven in the Solnhofen Archaeopteryx fossils were unearthed. Archaeopteryx size as a crow. It retains many features of reptiles: for example, mouth with teeth, like modern birds rather than the formation of horny beak; there is a composition by the 21 caudal long tail; forelimb three metacarpal from each other, not carpal metacarpal into healing, fingers with claws; no gas inside the bone nest; and so on. On the other hand, it has a feather, and have primary feathers, secondary feathers, tail feathers and feather re-differentiation, which are all characteristics of birds. In addition, it is in some skeletal form also showed some other bird features or transitional features, such as it is already the third metacarpal and wrist healed, but the second and the first metacarpal bone is not healed, so some scientists think that this is a reflection of birds into the carpal metacarpal metacarpal bone are the beginning of healing. Because reptiles, birds, characterized by the features in the basis of evolution, developed, so it was dubbed the bird is "glorified reptiles." It is also because Archaeopteryx skeleton structure and is called a virtual bone dragon small carnivorous theropod dinosaurs are very similar, has long been considered the origin of birds in the virtual bone dragons, birds, and speculated that the high metabolic level is Those dinosaurs inherited, some small carnivorous dinosaur that may already be a warm-blooded animals. Some even speculated that the beginning of the development of feathers and flight is not necessarily related to its original theropod dinosaurs may have been widespread. Archaeopteryx retained from a series of similar characteristics with the reptiles can be seen, all aspects of its structure to adapt to fly far from perfect, so presumably it is probably still only in the low altitude gliding. So, Archaeopteryx is how to walk from land into the sky glide in it? Scientists have two opinions. One view was that it had a good run of animals. From start to run, run using the forelimbs to beat the air to speed up the pace, this time on the forelimb feathers from the scales into the original type of variation to adapt to this habit in the process of gradually improving, and ultimately developed feathered wings, starting from the wings flutter and glide off the ground into the air. This theory is called the origin of bird flight, "said running." Another view was that Archaeopteryx was originally arboreal, and in the trees using feathered wings gliding is an enabling activities, which makes the scales on the forelimbs into the type of variation of the original feathers get more survival and breeding opportunities, and finally develop into feathered wings and gain the ability to fly. This theory is called the origin of bird flight "arboreal said." Later, according to the first five Archaeopteryx specimens of view, it not only has claws on its wings, after the end of the toe is also sharp, curved claws. Detrimental to the running of this claw, while climbing trees beneficial. This seems to support arboreal said. pets question and answers,www.5d2d.com
pets question and answers,www.5d2d.com
pets question and answers,www.5d2d.com
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