snjk-
百万年前,恐龙统治着地球.而后,恐龙灭绝了.究竟发生了什么?我们知道它们不是突然灭绝的,而可能是在几百万年间全部灭绝的.恐龙生存的年代,整个地球的气候温暖潮湿,有许多丛林.然而,地球的气候不断逐渐改变.当一些地域的气候变得寒冷干燥时,这部分的丛林便死去了.恐龙无从觅食物.这可能是恐龙灭绝的原因之一.
Millions of years ago, the dinosaurs(恐龙) ruled the earth. Since then, there have been no dinosaurs. What happened to then? We know they did not all die at once. It may have taken a few million years for all of them to die. In the days of the dinosaurs, the whole earth was warm and wet. There were many green jungles(丛林). But the earth changes slowly, all the time. When parts of the earth became cold and dry, the jungles there died. Then dinosaurs could not find enough to eat. This must be on reason why the dinosaurs died out.
余辉-
恐龙
（英文：dinosaur）是群中生代的多样化优势脊椎动物，属于爬行动物，但能直立行走，支配全球陆地生态系统超过1亿6千万年之久。恐龙最早出现在2亿4千5百万年前的三叠纪，灭亡于约6千5百万年前的白垩纪晚期所发生的白垩纪末灭绝事件。恐龙最终灭绝于6300万年前的新生代第三纪古新世。
在1862年发现的始祖鸟化石，与美颌龙化石极度相似，差别在于始祖鸟化石有着羽毛痕迹，这显示恐龙与鸟类可能是近亲。自恐龙复原图从1970年以来，许多研究指出现代鸟类极可能是兽脚亚目恐龙的直系后代。大部分科学家视鸟类为唯一幸存发展至今的恐龙，而少数科学家甚至认为它们应该分类于同一纲之内。鳄鱼则是另一群恐龙的现代近亲，但两者关系较恐龙与鸟类远。恐龙、鸟类、鳄鱼都属于爬行动物的初龙类演化支，该演化支首次出现于晚二叠纪，并在中三叠纪成为优势动物群。
在20世纪前半期，科学家与大众媒体都视恐龙为行动缓慢、慵懒的冷血动物。但是20世纪70年代开始的恐龙文艺复兴，提出恐龙也许是群活跃的温血动物，并可能有社会行为。近期发现的众多恐龙与鸟类之间关系的证据，支持了恐龙温血动物的假设。
[编辑本段]恐龙分类
恐龙属于:真核域---动物界---脊索动物门------脊椎动物亚门-------蜥形纲----初龙下纲-----双孔亚纲。
其在生物学上为一个总目。
恐龙与其它爬行动物的最大区别在于它们的站立姿态和行进方式,恐龙具有全然直立的姿态，其四肢构建在其体躯的正下方位置。这样的架构要比其他种类的爬行动物（如鳄类其四肢向外伸展），在走路和奔跑上更为有利。根据恐龙腰带的构造特征不同，可以划分为两大类：蜥臀目（Saurischia）和鸟臀目(Ornithischia)。
二者区别在于其腰带结构： 蜥臀目的腰带从侧面看是三射型，耻骨在肠骨下方向前延伸，坐骨则向后延伸，这样的结构与蜥蜴相似；鸟臀目的腰带，肠骨前后都大大扩张，耻骨前侧有一个大的前耻骨突，伸在肠骨的下方，后侧更是大大延伸与坐骨平行伸向肠骨前下方。因此，骨盆从侧面看是四射型。不论是蜥臀目还是鸟臀目，它们的腰带在肠骨、坐骨、耻骨之间留下了一个小孔，这个孔在其它各个目的爬行动物中是没有的。正是这个孔表明，与所有其它各个目的爬行动物相比，被称为恐龙的这两个目之间有着最近的亲缘关系。
蜥臀目分为蜥脚类(Sauropoda)和兽脚类(Theropoda)。
蜥脚类又分为原蜥脚类和蜥脚形类。原蜥脚类主要生活在晚三叠纪到早侏罗纪，是一类杂食--素食性的中等大小恐龙。蜥脚形类主要生活在侏罗纪和白垩纪。它们绝大多数都是巨型的素食恐龙。头小，脖子长，尾巴长，牙齿成小匙状。蜥脚亚目的著名代表有产于我国四川、甘肃晚侏罗纪的马门溪龙，由19节颈椎组成的脖子长度约等于体长的一半。
兽脚类生活在晚三叠纪至白垩纪。它们都是肉食龙，两足行走，趾端长有锐利的爪子，头部很发达，嘴里长着匕首或小刀一样的利齿。霸王龙是著名代表。
鸟臀目分为5大类：鸟脚类(Ornthopoda)、剑龙类(Stegosauria)、甲龙类(Ankylosauria)，角龙类(Ceratopsia)和肿头龙类(Pachycephalosauria)。
鸟脚类是鸟臀类中乃至整个恐龙大类中化石最多的一个类群。它们两足或四足行走，下颌骨有单独的前齿骨，牙齿仅生长在颊部，上颌牙齿齿冠向内弯曲，下颌牙齿齿冠向外弯曲。它门生活在晚三叠纪至白垩纪，全都是素食恐龙。例如：鸭嘴龙、禽龙等。
剑龙类，四足行走背部具有直立的骨板，尾部有骨质刺棒两对，剑龙类主要生活在侏罗纪到早白垩纪，是恐龙类最先灭亡的一个大类。其代表有被认为是居住在平原上的剑龙，被发现于东非坦桑尼亚的肯龙。
甲龙类的恐龙体形低矮粗壮，全身披有骨质甲板，以植物为食，主要出现于白垩纪早期。
角龙类，是四足行走的素食恐龙。头骨后部扩大成颈盾，多数生活在白垩纪晚期，我国北方发现的鹦鹉嘴龙即属角龙类的祖先类型。
肿头龙类主要特点是头骨肿厚，颥孔封闭，骨盘中耻骨被坐骨排挤，不参与组成腰带，主要生活在白垩纪。
恐龙灭绝
恐龙灭绝的原因新说:
1瘟疫后恐龙蛋受侵变质无法孵化
2小行星撞击地球
3哺乳动物变强，恐龙变衰
4气候变冷
5因哺乳动物偷吃恐龙蛋，使恐龙无法繁衍下一代
6有些人认为，在远古时期，彗星撞到地球，使地表发生巨大变化，让恐龙无法适应这种环境，导致灭绝。
其中2、6可归为一种学说，即天体撞击说。
3、5也可归为一种学说，哺乳动物进化说。
这些学说至今尚未定论，究竟谁对谁错，孰是孰非，都需要更多的证据。
恐龙 (Dinosaur)这个词字面上的意义是「可怕的蜥蜴」。这个词是由英国解剖学家理查欧恩爵士(1804-1892)所创造，用来描述不符合现今生物的化石遗骸。其中多数肉食恐龙长有羽毛。
恐龙是出现于二亿四千五百万年前，并繁荣至六千五百万年前结束的中生代爬行动物。或为恐龙和与它同一时代的蛇颈龙、翼龙等的模糊总称。恐龙在6300万年前(白垩纪结束,第三纪开始的时候)的时候突然全部消失，成为地球生物进化史上的一个谜，这个谜至今仍无人能解。地球过去的生物，均被记录在化石之中。中生代的地层中，即曾发现许多的恐龙化石。其中可以见到大量呈现各式各样形状的骨骼。但是，在紧接着的新生代地层中，却完全看不到恐龙的化石。由此推知恐龙在中生代时一起灭绝了。但是最新的研究表明：有一小部分恐龙可能在那次大灭绝中幸存了下来。最后因为不适应寒冷干燥的气候，而灭绝了。
恐龙种类多，体形和习性相差也大。其中个子大的，可以有几十头大象加起来那么大；小的，却跟一只鸡差不多。就食性来说，有温顺的草食者和凶暴的肉食者，还有荤素都吃的杂食性恐龙。
[编辑本段]灭绝原因
1.可能是因为小行星撞击或地壳运动带来的火山喷发或气候变化和食物不够。
2.可能是因为地表产生变化、植物变少，恐龙不适应环境变化，无法与在发展的鸟类哺乳动物争食物，慢慢从地球上消失了。
3.物种斗争说。恐龙年代末期，最初的小型哺乳类动物出现了，这些动物属啮齿类食肉动物，可能以恐龙蛋为食。由于这种小型动物缺乏天敌，越来越多，最终吃光了恐龙蛋。
4.大陆漂移说。地质学研究证明，在恐龙生存的年代地球的大陆只有唯一一块，即“泛古陆”。由于地壳变化，这块大陆在侏罗纪发生的较大的分裂和漂移现象，最终导致环境和气候的变化，恐龙因此而灭绝。
5.地磁变化说。现代生物学证明，某些生物的死亡与磁场有关。对磁场比较敏感的生物，在地球磁场发生变化的时候，都可能导致灭绝。由此推论，恐龙的灭绝可能与地球磁场的变化有关。
6.被子植物中毒说。恐龙年代末期，地球上的裸子植物逐渐消亡，取而代之的是大量的被子植物，这些植物中含有裸子植物中所没有的毒素，形体巨大的恐龙食量奇大，大量摄入被子植物导致体内毒素积累过多，终于被毒死了。
Dinosaur
(English: dinosaur) is a diversified group of Mesozoic vertebrates advantages are reptiles, but can walk upright, the dominant terrestrial ecosystems the world over 100 million 6 million years old. Dinosaurs first appeared 200 million in 1000 5 million years ago 4 of the Triassic, the demise of thousands of 5 to about 6 million years ago occurred in the Late Cretaceous extinction event at the end of the Cretaceous period. The ultimate extinction of the dinosaurs 6300 years ago in the Mesozoic and Cenozoic Tertiary Paleocene.
Found in 1862 in archeopteryx fossils, fossil jaw with the United States very similar archeopteryx difference is that fossil traces of a feather, indicating that dinosaurs and birds may be the next of kin. Since the dinosaurs recovery plans since 1970, many studies have pointed out that modern birds most likely suborder Theropoda a direct descendant of dinosaurs. Most scientists regard as the only surviving species of dinosaur now, but a small number of scientists even think that they should be classified within the same network. Another group of crocodiles is a close relative of modern dinosaurs, but the relationship between dinosaurs and birds is far more. Dinosaurs, birds, crocodiles are reptiles of the early evolution of long-type support,
The first time in the evolution of teams in the late Permian and Triassic become advantages in the fauna.
In the first half of the 20th century, scientists and the mass media as the dinosaurs such as the operations are slow, the cold-blooded lazy. However, the beginning of the 20th century, 70"s renaissance of the dinosaur, the dinosaur is perhaps the group of active warm-blooded animals, and there may be social behavior. Has found many relationship between dinosaurs and birds of the evidence to support the assumption that the dinosaurs warm-blooded animals.
[Edit this paragraph] dinosaur classification
Dinosaurs are: domain of eukaryotic animal kingdom --- --- ------ vertebrate chordate subphylum doors Lizard ARACHNIDA ------- ---- ----- Class of early lung subclass double.
In biology for a head.
Dinosaurs and other reptiles of the biggest difference is that their way of standing posture and the road, the dinosaur has a completely upright posture, the limbs to build in its location just below the Body. Such a structure than other types of reptiles (such as the crocodile-type stretching out its limbs), in walking and running on more favorable. Dinosaur belt in accordance with different structural characteristics, can be divided into two categories: hip Lizard Head (Saurischia) and the birds head butt (Ornithischia).
The difference between the two belts in its structure: The purpose of lizard hip belt from the side to see three radio type, below the pubic bone in the intestinal forward extension of the ischium extended backward, so that is similar to the structure and lizards; purpose bird hip belt, before and after iliac greatly expanding a suprapubic anterior pubic process before a large, stretched in the bottom of the ilium, the posterior is greatly extended in parallel with the ischium into the bottom of iliac ago. Therefore, the pelvis is in all directions from the side view type. Lizard Head whether hip hip or bird heads, and their belt in the ilium, ischium, pubis, a small hole between the left, this hole all the purpose in other reptiles is not. It is this hole show that
All purpose and all other reptiles than dinosaurs known as the head between the two most recent relationship.
Lizard Head buttocks into sauropod (Sauropoda) and type of animal feet (Theropoda).
Sauropod sauropod is divided into the former category and lizard-shaped pin. Sauropod mainly living in the original late Triassic to early Jurassic, is a kind of miscellaneous food - vegetarian of medium-sized dinosaurs. Lizard-shaped foot main living in the Jurassic and Cretaceous. The vast majority of them are vegetarian giant dinosaur. Head small, long neck, long tail, teeth into shape tsp. The purpose of a well-known sub-foot lizard on behalf of our country have produced in Sichuan, Gansu late Jurassic Mamenchisaurus, 19 cervical vertebrae from the neck of the composition of a length of about equal to half the body length.
Types of animal feet to live in the late Triassic period. They are all meat-long, two-legged walking long toe claws are sharp, well-developed head, long mouth, like a dagger or knife the利齿. On behalf of the famous Tyrannosaurus rex.
Hip birds head is divided into 5 categories: type of bird feet (Ornthopoda), Jianlong category (Stegosauria), a dragon type (Ankylosauria), Kok-long category (Ceratopsia) and Swollen Head Dragon Class (Pachycephalosauria).
Foot bird bird is the hip and the whole class of dinosaur fossils of the largest categories in a group. Their two-legged or four-legged walking mandibular teeth before a separate bone, only the growth in the cheek teeth, maxillary dental crown inward curved crown mandibular teeth bending outward. Its doors to live in the late Triassic period, dinosaurs are all vegetarian. For example: duck-billed dinosaur, such as Iguanodon.
Jian-long class, four-legged running back has a vertical plate of bone, tail bone stabbed two pairs of rods, swords dragon living in the major Jurassic to Early Cretaceous, the first type of dinosaur extinction is a major category. Their representatives have been considered to be living in the plains dragon sword, was found in Tanzania, East Africa is willing to Long.
A class-long dinosaur shape low sturdy, all wearing deck has bone to plants for food, mainly in the early Cretaceous period.
Kok-long, there are the four-legged vegetarian dinosaur walking. Neck into the skull to expand the rear shield, the majority living in the late Cretaceous period, found in northern China Psittacosaurus is an ancestor category Kok-long type.
Swelling the first major feature of Dragon swollen thick skull,颥hole closed after bone ischial symphysis was excluded, not to participate in the composition of belt, mainly living in the Cretaceous.
[Edit this paragraph] the extinction of dinosaurs
The reasons for the extinction of dinosaurs, said:
After a plague invaded degenerating eggs can not hatch
2 asteroids colliding with Earth
3, strong mammals, dinosaurs change failure
4 cooling
5 because of mammals eating dinosaur eggs so that dinosaurs can not produce the next generation
6 Some people think that, in ancient times, a comet hit the Earth, so that a dramatic change of surface, so that the dinosaurs could not adapt to this environment, leading to extinction.
2,6 which can be classified as a theory, namely that the impact of celestial bodies.
3,5 also can be classified as a theory, evolution of mammals.
These doctrines have not yet been conclusive, what is right, charge, need more evidence.
二亿四千五百万年dinosaur is in the former, and prosperity before the end of the Mesozoic六千五百万年reptiles. Or for the dinosaurs and with it the same era plesiosaur, pterosaurs, such as the fuzzy term. Dinosaurs 6300 years ago in (the end of the Cretaceous period, the beginning of the Tertiary), when suddenly all disappeared, the history of biological evolution on Earth of a mystery, this mystery no one can answer so far. The Earth"s past life, were being recorded in the fossil. Mesozoic strata, which have found that many of the dinosaur fossils. One can see the shape of a large number of a variety of bones. However, in the immediate formation of a new generation,
Did not see the fossils of dinosaurs. This push to know when the dinosaurs in the Mesozoic with extinction. But the latest research shows that: there is a small part of that large dinosaurs may have survived the extinction. Finally, because cold and dry climate are not suited, and extinction.
Many kinds of dinosaurs, the difference between body shape and habits are also great. Big tall one, you can add up to dozens of big elephants; small, but almost with a chicken. On the diet, there are docile herbivores and the肉食者violent, and the omnivorous dinosaur荤素eat.
[Edit this paragraph] the reasons for extinction
1. May be due to crustal movement asteroid impact or volcanic eruption brought about by climate change and food or not enough.
2. May be due to changes in the surface, fewer plants, dinosaurs are not suited to environmental change, not the birds and mammals in the development for food, slowly disappeared from the Earth.
3. Species struggle. The end of the dinosaur era, the initial emergence of small mammals, these animals are rodents and predators may feed a dinosaur egg. As a result of this lack of natural predators of small animals, more and more and eventually finished the dinosaur eggs.
4. That the continental drift. Geological studies show that survival in the dinosaur age of the Earth"s only a piece of the mainland only, that is, "Pangea." As a result of changes in the earth"s crust, the continent occurred in the Jurassic of the larger phenomenon of division and drift, which eventually led to the environment and climate change, and therefore the extinction of dinosaurs.
5. Geomagnetic change that. Modern biology shows that certain biological and magnetic fields related to the death. More sensitive to the magnetic field of biology, the Earth"s magnetic field changes in time, may lead to extinction. It seems therefore that the extinction of dinosaurs may be related to changes in the earth"s magnetic field.
6. Angiosperms said poisoning. The end of the dinosaur era, the earth on the disappearance of gymnosperm gradually replaced by a large number of angiosperms, gymnosperms, these plants contain toxins that are not, a huge dinosaur body qi food, and a large number of intake of angiosperms led to the accumulation of toxins too much, was finally poisoned.
恐龙之最
最早的恐龙
美亚里桑那州硅化木公园发现一条距今2亿2千5百万年鸵鸟大小200磅最大的恐龙的恐龙化石。
最迟出现的恐龙
角龙类恐龙在白垩纪距今1亿3千5百万年以后最盛
最大的恐龙
据美国阿而伯克基地区发现的震龙全长39-----52米重达80吨。
最小的恐龙
新颌龙（体长60厘米，重5.5千克）
Dinosaur most
The earliest dinosaurs
The United States and Asia fossil woods Arizona Park found a 2-thousand two hundred million years ago 5 million years the size of two hundred pounds an ostrich"s largest dinosaur fossil dinosaur.
Appears at the latest dinosaur
Kok-long type of dinosaur in the Cretaceous period 100 million years ago 3, 1000 5 years after the height
Largest dinosaur
According to the United States and the Arab-Israeli region伯克基David Long found 39 ----- 52 meters in length weighing 80 tons.
The smallest dinosaur
New jaw long (body length 60 cm and weighs 5.5 kilograms)