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智科眼: 双语看懂新科研
演化 27
Mackerel(鲭鱼) sharks(鲨鱼) ((()Lamniformes(Lamniformes))()) are() a(a) group(群体) consisting(组成) of(of) some(一些) of(of) the most() iconic(标志性) sharks(鲨鱼) we(我们) know(),(,) including(包括) the mako(mako) shark(鲨鱼) ((()the fastest(最快) shark(鲨鱼) in(in) the world(世界)),(),) the infamous(臭名昭着) great() white() shark(),(,) and() Megalodon(Megalodon),(,) the biggest(最大) predatory(掠食) shark(鲨鱼) that(that) has(has) ever(曾经) roamed(漫游) ( ) the world(世界)'s('s) oceans(海洋).(.) An(An) international(国际) team(团队) of(of) researchers(研究) around(around) Patrick(帕特里克) L(L.) .(.) Jambura(Jambura) from(from) the University(大学) of(of) Vienna(维也纳) found(发现) a(a) unique(独特) feature(特征) in(in) the teeth(牙齿) of(of) these(这些) apex() predators(食肉动物),(,) which(which) allowed(使) them(它们) to(to) trace(追溯) back(back) the origin(起源) of(of) this(这一) group(群体) to(to) a(a) small() benthic(底栖) shark(鲨鱼) from(from) the Middle() Jurassic(侏罗) (165((165) mya(mya)).().) Their(他们) study(研究) was(was) recently(最近) published(发表) in(in) the journal(学报) Scientific(科学) Reports(报告).(.)
Similar(相似) to(to) humans(人类),(,) shark(鲨鱼) teeth(牙齿) are(are) composed(组成) of(of) two(两种) mineralized(矿化) structures(结构):(:) a(a) hard() shell() of(of) hypermineralized(超矿化) tissue(组织) (in((in) humans(人类) enamel(珐琅质),(,) in(in) sharks(鲨鱼) enameloid())()) and() a(a) dentine(牙本质) core(核心).(.) Depending(根据) on(on) the structure(结构) of(of) the dentine(牙本质) we(我们) distinguish(区分) between(between) two(两种) different(不同) types(类型):(:) orthodentine(orthodentine) and() osteodentine(osteodentine).(.)
Orthodentine(Orthodentine) has(has) a(a) very(非常) compact(紧凑) appearance(外观) and() is(is) similar(类似) to(to) the dentine(牙本质) we(我们) can(可以) find(找到) in(in) human(人类) teeth(牙齿).(.) In(In) shark(鲨鱼) teeth(牙齿),(,) orthodentine(orthodentine) is() confined(限制) to(to) the tooth(牙齿) crown(牙冠).(.) In(In) contrast(),(,) the other(other) dentine(牙本质) type(类型) is() spongious(海绵状的) in(in) appearance(外观) and(并且) resembles(类似) real(真正) bone(骨质) and() therefore(因此) is() called(称为) osteodentine(骨桥蛋白).(.) It() can(可以) be(be) found(找到) in(in) the root(牙根),(,) anchoring(固定) the tooth(牙齿) to(to) the jaw(颌骨) and() in(in) some(某些) species(物种) also() in(in) the tooth() crown(牙冠) where(where) it(it) supports(支撑) the orthodentine(矫正).(.)
Using(使用) high resolution(高分辨) CT(CT) scans(扫描),(,) Patrick(帕特里克) L(L.) .(.) Jambura(Jambura) and() his(他的) colleagues(同事) examined(检查) the tooth(牙齿) composition(组成) of(of) the great() white() shark() and its(及其) relatives(亲属) and() found(发现) a(a) peculiar(特殊) condition(状况) of(of) the teeth(牙齿) of(of) members(成员) of(of) this(这一) group():(:) the osteodentine(骨桥蛋白) of(of) the roots(根部) intrudes(侵入) into(into) the crown(牙冠) and() replaces(取代) the orthodentine(矫形) there(那里) completely(完全),(,) making(making) it(it) the only(唯一) type(类型) of(of) dentine(牙本质) being(being) present(当前).(.) This(这种) condition(情况) is(is) not() known() from(from) any(任何) other(其他) shark(鲨鱼),(,) which(which) all(all) possess(具有) orthodentine(齿) to(to) some(某种) degree(程度) and() thus(因此) it() is(is) confined(限于) to(to) members(成员) of(of) this(这个) group().(.)
Another(另一个) species(物种) that() was() examined(检查) was() the fossil(化石) shark() Palaeocarcharias(Palaeocarcharias) stromeri(stromeri),(,) which(which) is(is) well(well)-()represented(表示) by(by) complete(完整) skeletons(骷髅) from(from) the famous(著名) 150(150) million(亿) year old(年龄) Solnhofen(Solnhofen) Plattenkalks(Plattenkalks) of(of) South(南部) Germany(德国).(.) The oldest() find(发现) of(of) this(这个) species(物种) is(is) from(from) the Middle() Jurassic(侏罗) (165((165) million(亿) years ago(多年前))()) and() it() didn(没有)'t('t) have(have) much(much) in(in) common(共同) with(with) today(今天)'s('s) mackerel(鲭鱼) sharks(鲨鱼).(.) Palaeocarcharias(Palaeocarcharias) was() a(一种) small() sluggish() benthic(底栖) shark(鲨鱼),(,) not exceeding(不超过) lengths(长度) of(of) more than(超过) a(a) metre(),(,) that(that) seemingly(似乎) hunted(捕杀) small() fish() in(in) shallow waters(浅水).(.) To(To) this(这个) day(),(,) its(它的) affiliation(隶属关系) has(has) been(been) a(a) riddle() to(to) scientists(科学家),(,) since(因为) its(它的) body(身体) shape(形状) resembles(类似) a(a) carpet(地毯) shark(鲨鱼),(,) while(while) its(它的) fang()-()like() teeth(牙齿) are() similar() to(to) mackerel(鲭鱼) sharks(鲨鱼).(.) The examination(检查) of(of) the tooth(牙齿) microstructure(微观结构) yielded(产生了) the presence() of(of) the same(相同) unique(独特) tooth(牙齿) composition(组成) that() is(is) found(发现) only() in(in) great() white() sharks() and() their(他们的) relatives(亲属).(.) The shared(共同) tooth(牙齿) histology(组织学) is() a(一个) strong(强有力) indicator(指标) that() this(这个) small() inconspicuous() shark(鲨鱼) gave(给予) rise() to(to) one(one) of(of) the most() iconic(标志性) shark(鲨鱼) lineages(血统) that(that) includes(包括) giants(巨人) like(like) the extinct(灭绝) Megalodon() or() the living(生活) great() white() shark().(.)
"(")Orthodentine(Orthodentine) is(is) known(闻名) for(for) almost(几乎) all(所有) vertebrates(脊椎动物)()from() fish(鱼类) to(to) mammals(哺乳动物),(,) including(包括) all(所有) modern(现代) sharks(鲨鱼),(,) except for(除了) the mackerel(鲭鱼) sharks(鲨鱼).(.) The discovery(发现) of(of) this(这种) unique(独特) tooth(牙齿) structure(结构) in(in) the fossil(化石) shark(鲨鱼) Palaeocarcharias(Palaeocarcharias) strongly(强烈) indicates(表明) that(that) we(我们) found(发现) the oldest() known(已知) ancestor(祖先) of(of) the great(重大) white() shark() and() shows(表明) that(that) even(即使) this(这种) charismatic(魅力) giant(巨型) shark() started(开始) on(on) a(a) shoestring(鞋带),"(,") says() Patrick(帕特里克) L.(L.) Jambura(Jambura).(.)

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