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Sorry, but the T. rex doesnt look anything like you think it does
With a revelation that threatens to ruin some childhood toys or a Jurassic Park rewatch, paleontologists have given one of the most famous dinosaurs a facelift, proposing that the Tyrannosaurus did not sport ferocious, protruding chompers, but proportionally sized teeth concealed by a set of scaly, lizard-like lips.
In a new study out of the University of Portsmouth, an international team of researchers studied the jaw morphology, tooth structure and dental wear patterns of lipped and lipless reptiles, and found that theropod mouths looked and functioned more like those of lizards than of crocodiles, as previously thought.
“Although it’s been argued in the past that the teeth of predatory dinosaurs might be too big to be covered by lips, our study shows that, in actuality, their teeth were not atypically large,” said study leader Thomas Cullen, assistant professor of paleobiology at Auburn University. “Even the giant teeth of tyrannosaurs are proportionally similar in size to those of living predatory lizards when compared for skull size, rejecting the idea that their teeth were too big to cover with lips.”
In fact, the scientists believe their mouth structure resembled a tuatara, the small extant New Zealand lizard-like reptile that was around at the time of the dinosaurs. It also had a lot in common with some lizards, none of which were close relatives of the theropods.
“It’s quite remarkable how similar theropod teeth are to monitor lizards,” said study co-author Derek Larson, Collections Manager and Researcher in Palaeontology at the Royal BC Museum in Canada. “From the smallest dwarf monitor to the Komodo dragon, the teeth function in much the same way. So, monitors can be compared quite favorably with extinct animals like theropod dinosaurs based on this similarity of function, even though they are not closely related.”
The study points out that the dinosaurs’ skulls and teeth were relative in size to those of modern lizards with lips. Also, examining fossils, scientists found that the holes in the theropod jaws that would have housed nerves and blood for mouth tissue were far more like those in a lizard than of a crocodile.
“As any dentist will tell you, saliva is important for maintaining the health of your teeth,” said co-author Kirstin Brink, assistant professor of paleontology at the University of Manitoba. “Teeth that are not covered by lips risk drying out and can be subject to more damage during feeding or fighting, as we see in crocodiles, but not in dinosaurs.
“Dinosaur teeth have very thin enamel and mammal teeth have thick enamel (with some exceptions),” she added. “Crocodile enamel is a bit thicker than dinosaur enamel, but not as thick as mammalian enamel. There are some mammal groups that do have exposed enamel, but their enamel is modified to withstand exposure.”
While the study offers fresh insights into how the animals may have fed and maintained dental health, it also offers evolutionary ecologists some exciting new avenues of exploration and artists the option of going back to the drawing board.
“Dinosaur artists have gone back and forth on lips since we started restoring dinosaurs during the 19th century, but lipless dinosaurs became more prominent in the 1980s and 1990s,” said co-author Mark Witton from the University of Portsmouth. “They were then deeply rooted in popular culture through films and documentaries – Jurassic Park and its sequels, Walking with Dinosaurs and so on.
“Curiously, there was never a dedicated study or discovery instigating this change and, to a large extent, it probably reflected preference for a new, ferocious-looking aesthetic rather than a shift in scientific thinking,” he added. “Were upending this popular depiction by covering their teeth with lizard-like lips. This means a lot of our favorite dinosaur depictions are incorrect, including the iconic Jurassic Park T. rex.”
注释：
Jurassic Park
表示" 侏罗纪公园（电影名）"，Jurassic 表示“ 侏罗纪”，如：The Jurassic formation is drilled through. 侏罗系地层已钻穿。
paleontologist： n
表示"古生物学者"，means "a specialist in paleontology"，如：
facelift: v; n
表示" 整容"，means ""，如：If I got a facelift, I could shave fifteen years off my age. 我若做一次整容，看上去可年轻15 岁。
Tyrannosaurus: n
表示" [古生物]暴龙"，如：One of the biggest dinosaurs was tyrannosaurus rex. 暴龙是体型最大的恐龙之一。
ferocious: adj
表示"残忍的；凶猛的"，means " fierce;cruel;savage"，如：The ferocious chieftain was executed.那个凶残的匪首被处决了。
chomper： n
表示"使劲咀嚼者"，chomp表示“大声地咀嚼；如：We really get annoyed when foreigners try to chomp on chicken feet. 我们真的很讨厌外国人咬鸡爪子时的样子。
scaly： adj
表示" 有鳞的"，means "covered with scales or scurf"，如：The reptiles skin is tough and scaly. 这种爬行动物的皮肤坚韧并带有鳞屑。
morphology: n
表示" (生物学或语言学里的)形态学"，如：They usually differ markedly in morphology. 它们在形态学上是有明显不同的。
Theropod: n
表示" 兽脚亚目食肉恐龙(前肢小；主要用后肢行走)"，means ""，如：The palaeontologist claimed that he had found a unique dinosaur fossil but it turned out to be a mares nest. 一位古生物学家声称，他已发现了一块罕见的恐龙化石，但结果根本不存在。
predatory: adj
表示" 掠夺的；捕食生物的"，means ""，如：We were pestered by predatory salesmen. 贪心的商人敲了我们竹.
atypical: adj
表示" 非典型的；"，如：He was an atypical English schoolboy. 他是一个非典型的英国男学生。
paleobiology: n
表示" 古生物学"，means "a branch of paleontology that deals with the origin and growth and structure of fossil animals and plants as living organisms"，如：And don‘t be put off just because you don‘t quite know what immunology， paleobiology， international development studies， ethnomusicology， or civil engineering are . 不要因为你不是很清楚什么是免疫学专业，古生物专业，国际发展研究专业，民族音乐学或是土木工程，而排除这些专业。
tuatara: n
表示" (新西兰产的)大蜥蜴"，如：A prehistoric reptile, tuatara, has been found nesting in New Zealand. 一种史前爬行类动物，在纽西兰发现它们的巢穴。
extant: adj
表示"现存的"，means "still in existence"，如：This law is ancient but still extant. 这一法律古老但仍然有效。
Komodo: n
表示" [动](印尼)巨蜥"，如：Komodo Dragons live for about 20 years. 科摩多巨蜥的寿命约为20年。
saliva: n
表示"唾液"，如：Saliva is secretion of the salivary glands. 唾液是唾液腺的分泌物。
enamel: n
表示" 搪瓷；珐琅；瓷釉"，如：The pots are made with blue enamel. 这些锅上有蓝色的搪瓷。
mammalian: n; adj
表示" 哺乳动物(的）"，如：The report is on mammalian thermoregulation. 那份报告是有关哺乳动物的体温调节。
aesthetic： adj
表示"审美的"，means "concerning aesthetics"，如：Later he also gained in aesthetic knowledge. 后来他的美学知识也增加了。
中文简要说明：
6500万年前的暴龙(Tyrannosaurus rex,也称霸王龙，简写T-REX)，被认为是地球史上最勇猛的猎食者，也最符合我们对上古巨兽的想象，在各种还原艺术画当中，暴龙即使闭着嘴，也外露着巨大尖牙。然而新的研究认为，这种想象可能并不正确，虽然暴龙确实有一口好牙，但是当它闭嘴时，牙齿应该没有外露，换言之，暴龙没有暴牙。
新阿特拉斯报导，包括《侏罗纪公园》这部经典科幻片，暴龙即使不张嘴也是令人不含而栗，因为它森森的白牙就露在外面。这种还原图其实是参考鳄鱼的形态，但是英国朴兹茅斯大学(University of Portsmouth)的一项新研究认为，比对了有唇和无唇爬行动物的颌骨形态、牙齿结构和牙齿磨损模式，兽脚类恐龙的嘴部外观与功能都更像蜥蜴，而不是鳄鱼。即使是肉食蜥蜴，牠们在闭嘴时，并没有牙齿外露。
古生物学助理教授柯林(Thomas Cullen)是这个研究团队的主持人，他说：虽然过去有人认为，掠食性恐龙的牙齿可能太大，而无法被嘴唇遮盖，但我们的研究表明，这只是视觉上的错觉，实际上，它们的牙齿并没有异常大。 与头骨大小相比，霸王龙的牙齿固然很大，但是它的头也很大；与现存的掠食性蜥蜴的头部-牙齿比例是相似的，这否定了它们因为牙齿太大而无法被嘴唇覆盖的设想。」
加拿大皇家不列颠哥伦比亚博物馆古生物学藏品经理兼研究员拉尔森(Derek Larson)说：「兽脚类恐龙的牙齿与蜥蜴的牙齿非常相似，从最小的侏儒巨蜥，到最大的科莫多巨蜥，牙齿的功能几乎相同。因此，基于功能的相似性，可以将巨蜥与兽脚亚目恐龙等已灭绝动物，进行相关性比较，尽管它们并不是密切相关的。」
研究指出，恐龙的头骨和牙齿的大小比例，与现代蜥蜴的嘴唇相似。此外，科学家在检查化石时发现，兽脚亚目下颚上的孔洞，更像是蜥蜴的孔洞，而不是鳄鱼的孔洞。
还有一个常识性问题，就是「闭上嘴比较健康」，加拿大马尼托贝大学(University of Manitoba)的助理教授布尔克(Kirstin Brink)说：「正如任何牙医都会叮嘱的那样，唾液对于维持牙齿健康很重要，没有被嘴唇覆盖的牙齿，有变干的风险，并且在进食或打斗时，都可能会受到更大的伤害，鳄鱼是因为在水里，所以比较没有这样的问题，但是恐龙脸是一直在干燥的环境。」
布尔克补充：「爬行动物的牙釉质非常薄，而哺乳动物的牙釉质很厚，鳄鱼牙釉质比恐龙牙釉质厚一点，但没有哺乳动物牙釉质厚。有些哺乳动物确实有暴露的牙釉质，但它们的牙釉质经过改造可以承受暴露。恐龙的化石证明，它们牙齿的牙釉质也像爬行动物，不能持续在环境中暴露。」
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