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2006-11-24 4:42 am
鯊魚的祖先:鯊魚在地球上生存了大約3億5千萬年到4億年之間,比恐龍都來得久遠,但在近 1億年間則變化不大。鯊魚的始祖具有利齒和背刺,表皮上的盾鱗比軟骨更易形成化石。目前已知的最原始的鯊魚是裂口鯊(於美國俄亥俄州的古生代地層發現),擅長游泳及捕獵,身長有2公尺,背刺前長有2個背鰭,尾形對稱,骨骼則不對稱,牙齒呈磨平狀,無法再生,與現代的鯊魚差異甚大,當時也有小型鯊的存在,但是由於牠們敏捷的速度,往往使牠們在當時的巨魚環伺下,仍能存活至今...和人類歷史最近的大白鯊祖先化石(6500萬年前),長約13公尺,牙齒約有一個手掌大。
世界上約有380種鯊魚,共分八目三十科,約有27種會攻擊人類,12種可能會攻擊人類,還有12種因為體型和習性的關係,可能具有危險性,出現於台灣地區附近海域者約90種。並非每種鯊魚都呈流線型,琵琶鮫的身體呈扁平,虎鯊的頭部為鈍形,竹鯊的身體為長型。鯊魚八目中包括了六鰓形目、鼠鯊形目、真鯊形目、虎鯊形目、扁鯊形目、鬚鯊形目、角鯊形目、鋸鯊形目。其中真鯊形目和角鯊形目就佔了全部種的77﹪,真鯊形目獨佔56﹪。


中文名稱:鯊魚

英文名稱:shark

回答 (2)

2006-11-25 11:05 pm
✔ 最佳答案
An ancestor of a shark: I live, and I all than a dinosaur stand out, and, as for about 300,005,000 many years, a shark change into a thing of the face of the Earth too much for a long time between 400,000,000 years when but I do it for near 100,000,000 years. The founder of a shark freezes with benefiting a tooth and the splinter which I recited, and a scale of a shield on a cuticle changes that I form a fossil more than cartilage. A shark of the most beginning to already know it for the present catches hunting with a goby (stratum is found for the Paleozoic era of a state of American Ohio) of a slit, and swimming grows, and there are 2 meters to height, and call itself it by mistake when Seoi does Ogata symmetry, a frame in there being two dorsal fins in the head before a splinter, and present that a tooth polishes form in usual times, and is very big, and, in reproduction inability, existence of a mini-goby is similar to a shark difference in the present age in those days; and then in speed that correct it, and is agile by them, them in many cases; let 巨魚環伺下 be; can save that still give life in now... With a clear goby ancestor fossil (before 6500 many years) of human history these days, I promise 13 meters for a long time, and a tooth promises that there is size of one palm.
380 kinds of sharks promise a certain thing on the world, and divide 30 courses of eight eyes and promise that combination attacks that there are 27 kinds and shoots the human, and combination attack enables that 12 kinds shoot the human, and 12 kinds of figures and habits still have relation and can have danger, and it appears to promise 90 kinds for a person of sea area of Taiwan district neighborhood. All each sharks do not present a streamline at all, and a body of a shark of a biwa presents flat なを, and, as for the head of a goby of a tiger, a body of a bamboo goby decides to grow a model as dull form. The whole eyes of 8 of a shark contains eyes of form of six gills, and it is-shaped eyes,-shaped eyes of a true goby of a mouse shark,-shaped eyes of a goby of a tiger,-shaped eyes of a goby of 扁,-shaped eyes of a goby of 鬚,-shaped eyes of a corner goby,-shaped eyes of a goby of a saw. Eyes of form of a true goby of those and eyes of form of a corner goby occupy 77% that all wound up immediately, and-shaped eyes of a true goby monopolize 56%.
2006-11-24 4:44 am
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參考: 文獻


收錄日期: 2021-04-25 17:40:01
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