What ate dinosaurs?

　　誰吃了恐龍

　　Old crocs

　　古鱷魚

　　Even in their heyday, dinosaurs were not quite as dominant as popular myth makes them outto be

　　即便是在全盛時期，恐龍并非像民間傳說所理解的那樣占絕對統(tǒng)治地位

　　ONE answer to the question, What ate dinosaurs? is, obviously, Other dinosaurs. The ropodpredators like Tyrannosaurus and Allosaurus loom large in the imagination of every lover ofprehistoric monsters, and their animatronic fights with the likes of Diplodocus andStegosaurus are the stuff of clich. Science, though, tries to look beyond the obvious, and atthis years meeting of the Society of Vertebrate Palaeontology, held in Las Vegas, some of thespeakers asked whether the top predators of the Mesozoic era really were all dinosaurs. Theirconclusion was no. Another group of reptiles, until recently neglected, were also importantcarnivores. And it is a group that is still around today: the crocodiles.

　　誰吃恐龍很明顯，其中一個答案是：其它恐龍每個史前怪獸愛好者的腦海里浮現(xiàn)出的是像霸王龍、翼龍這樣的獸腳類掠食者，電腦制作的它們與梁龍、劍龍的打斗也成為俗套。而科學試圖不落窠臼。今年，在拉斯維加斯召開的古脊椎生物學會會議上，一些發(fā)言人問到中生代頂級掠食者是否全是恐龍，結論是否。直到最近還被忽視的一類爬蟲，同樣是重要的食肉動物，正是仍然存活于今的一個族群：鱷魚。

　　That the past role of crocodiles has been underestimated wassuggested a few years ago by Paul Sereno. Dr Sereno, a palaeontologist at the University ofChicago, uncovered a crocodile-dominated ecosystem from about 100m years ago , in what is now north Africa. Besides water-dwelling giants similar to todays animals, he found a range of forms including vegetariansand species that ran on elongated legsmore like dogs than crocodiles. That discovery hasprompted other fossil hunters to look elsewhere. As a result, even the well-studied rocks ofNorth America are revealing that dinosaurs did not have it all their own way in the ecosystemsof the Mesozoicas Stephanie Drumheller of the University of Iowa and Clint Boyd of theUniversity of Texas at Austin explained to the meeting.

　　幾年前，芝加哥大學古生物學家保羅?賽倫諾博士提出鱷魚過去的角色被低估了，在今天的北非，他發(fā)現(xiàn)了一個一億年前由鱷魚占主導地位的生態(tài)系統(tǒng)。除了與現(xiàn)代鱷魚同為水生巨獸外，他還發(fā)現(xiàn)了一系列包括食草的、用長腿行走的比起鱷魚來更像狗的種群及形態(tài)。這一發(fā)現(xiàn)促使其他化石探尋者著眼于其它地方。結果是，即便是那些出自北美的已經(jīng)研究得很透徹的化石也顯示出恐龍并非占據(jù)中生代生態(tài)系統(tǒng)全部位置。正如衣阿華大學的斯蒂芬妮?莊姆海勒以及位于奧斯汀的德克薩斯大學的克林特?博依德在會上說的那樣。

　　The Cretaceous equivalent of zebra and antelopesthe victim species in every wildlifedocumentary about the dramas of the African savannahwere herbivorous dinosaurs calledornithopods. Frequently, these were taken by theropods. But not always. When Ms Drumhellerand Mr Boyd examined the bones of juvenile upper-Cretaceous ornithopods dug up in Utahthey saw marks on one skeleton that looked suspiciously like those modern crocodiles inflictwhen biting and tearing at their prey. On examining these marks more closely, they found acrocodilian tooth stuck in one of them.

　　白堊紀被稱為鳥腳亞目食草恐龍其地位相當于斑馬和羚羊每部有關非洲大草原的紀錄片中被捕殺的種群。這些恐龍經(jīng)常被獸腳亞目食肉恐龍捕食。但不總是這樣，當莊姆海勒與博依德對猶他州出土的白堊紀年幼的鳥腳亞目食草恐龍的化石進行檢查時，他們在一副骨架上發(fā)現(xiàn)了看上去像是遭受現(xiàn)代鱷魚撕咬的痕跡。在對這些痕跡進一步檢查后，他們發(fā)現(xiàn)一顆鱷魚目動物牙齒嵌在其中一塊骨頭上。

　　Crocodile tears

　　鱷魚的眼淚

　　It was not a large tooth. Its size suggests the animal which made it was no more than a metreand a half long. Such a predator would have been unable to take on an adultornithopod. Nevertheless, this tooth is the first unarguable proof that crocodilians did indeedsnack on dinosaurs. Moreover, it helps to confirm suspicions that the other crocodile-bite-likemarks that Ms Drumheller and Mr Boyd have discovered really are what they look like. Bycombining that with an analysis of the whole site, the two researchers argue that what theyhave discovered is a dinosaur nesting ground that was being raided by crocodilians.

　　這顆牙不是很大，其尺寸表明牙齒的主人不超過一米五這樣的掠食者本不能捕食一頭成年鳥腳亞目食草恐龍。但無可爭辯的是，這顆牙是第一個鱷魚目動物拿恐龍當點心的證據(jù)。此外，這也有助于消除對莊姆海勒與博依德發(fā)現(xiàn)的其它看似鱷魚咬痕的懷疑。結合對這個地區(qū)的分析，兩位研究者認為他們所發(fā)現(xiàn)的是一個遭到鱷魚目動物偷襲的恐龍筑巢地。

　　Such suspicions have been aroused before. Other sites in Utah are known to be dinosaurnesting grounds, since eggs are found there. Crocodilian bones frequently turn up at suchsites. Ms Drumheller and Mr Boyd, however, seem to have nailed the connection down. Juveniledinosaurs, at least, were indeed the prey of crocodilians. But what about adults?

　　這樣的懷疑以前也出現(xiàn)過。由于發(fā)現(xiàn)了恐龍蛋，人們知道猶他州還有其它恐龍筑巢地。在這些地區(qū)，鱷魚目動物化石經(jīng)常被發(fā)現(xiàn)。可莊姆海勒與博依德像是要明確這一關系，年幼恐龍至少是鱷魚目動物的獵物，那么成年的呢?

　　More than mere morsels

　　不僅僅是少數(shù)

　　To investigate that question, Martin Lockley at the University of Colorado, Denver, andSpencer Lucas of the New Mexico Museum of Natural History and Science, turned to one of themost famous fossil phenomena on the planetthe dinosaur freeway that runs throughColorado, New Mexico, Kansas and Oklahoma. This collection of tracks, scattered over severalsites of the same age along the coast of an inland sea, is thought to mark an ancientmigration route. The traces of more than 1,380 individual animals can be distinguished.Most, but not all, were ornithopods. Some were small carnivorous dinosaursthe sort thatmight pick off young stragglers in the way that the crocodilians identified by Ms Drumheller andMr Boyd did. But there is, Dr Lockley and Dr Lucas realised, something missing from thepicture. When they looked for traces of big predatory dinosaurs, they found none.

　　為了弄清這一問題，丹佛科羅拉多大學的馬丁?洛克里以及新墨西哥州自然歷史博物館的斯派瑟?盧卡斯將目光轉向世上最著名的化石現(xiàn)象之一橫穿科羅拉多、新墨西哥、堪薩斯、俄荷拉荷瑪?shù)目铸埞贰Ｓ谕荒甏刂粋€內(nèi)陸海海岸分布在數(shù)個地區(qū)，這一匯集恐龍蹤跡的地區(qū)被認為是標出了一條古老的遷徙路線。人們能區(qū)分出超過1380種不同動物的蹤跡。絕大部分是鳥腳亞目食草恐龍。一些是小型食肉恐龍正如莊姆海勒與博依德所確認的鱷魚目動物那樣，這些恐龍會截殺年幼離群的食草恐龍。但洛克里與盧卡斯博士明白，圖上遺漏了一些東西。當他們尋找大型掠食恐龍的線索時，他們什么也沒發(fā)現(xiàn)。

　　That is ecologically absurd. Unless, of course, the top predator of the systemthe one thatcould hunt down adult ornithopodswas not a dinosaur at all. And, when Dr Lockley and DrLucas re-examined the tracks they found that that was exactly what was going on. Instead oftheropod footmarks, they found those of crocodilians. More than a quarter of the places wherethe dinosaur freeway surfaces have yielded signs of crocs. And they were big: sometimes morethan four metres long. That is certainly large enough to take on an adult ornithopod.

　　從生物學上講，這是荒唐的。當然除非生態(tài)系統(tǒng)的頂級掠食者即是能捕殺成年的鳥腳亞目食草恐龍的并不完全是恐龍。而且，當洛克里與盧卡斯博士對這些線索進行重新檢查時，他們發(fā)現(xiàn)那正是曾經(jīng)所發(fā)生的。在出土的恐龍公路上，超過1/4的地區(qū)已發(fā)現(xiàn)鱷魚的蹤跡。而且它們很大：有時超過4米長，大到足以捕殺一頭成年鳥腳亞目食草恐龍。

　　Such megacrocs, then, could easily have acted as top predators in this ecosystem. But thatdoes not completely explain the absence of theropod tracks. Modern migrating herbivores fallvictim to many sorts of carnivore: big cats, wolves and hyenas, to name but three. Themarshy conditions of the dinosaur freeway may, though, have favoured crocodilians over predators that had evolved on drierland. In that sort of environment even a big theropod would constantly have been lookingover its shoulder. Perhaps the real reason why they did not plant their footprints on thedinosaur freeway is that they might have ended up as prey, as well.

　　這樣的巨鱷能在這樣的生態(tài)系統(tǒng)中輕松擔當頂級掠食者的角色。但這并不能完全解釋獸腳亞目食肉恐龍的缺位。現(xiàn)代遷徙類食草動物成為眾多食肉動物的犧牲品：大型貓科動物、狼、鬣狗，就拿這三樣來說。然而，比起在干燥陸地上進化的掠食者，恐龍公路所處的濕地環(huán)境也許更受鱷魚目動物歡迎。在那樣一種環(huán)境下，即便是一頭巨大的獸腳亞目食肉恐龍也會不時回頭張望。它們?yōu)楹螞]有在恐龍公路上留下足跡呢?真正的原因或許是它們同樣亡于其它掠食者。

　　What ate dinosaurs?

　　誰吃了恐龍

　　Old crocs

　　古鱷魚

　　Even in their heyday, dinosaurs were not quite as dominant as popular myth makes them outto be

　　即便是在全盛時期，恐龍并非像民間傳說所理解的那樣占絕對統(tǒng)治地位

　　ONE answer to the question, What ate dinosaurs? is, obviously, Other dinosaurs. The ropodpredators like Tyrannosaurus and Allosaurus loom large in the imagination of every lover ofprehistoric monsters, and their animatronic fights with the likes of Diplodocus andStegosaurus are the stuff of clich. Science, though, tries to look beyond the obvious, and atthis years meeting of the Society of Vertebrate Palaeontology, held in Las Vegas, some of thespeakers asked whether the top predators of the Mesozoic era really were all dinosaurs. Theirconclusion was no. Another group of reptiles, until recently neglected, were also importantcarnivores. And it is a group that is still around today: the crocodiles.

　　誰吃恐龍很明顯，其中一個答案是：其它恐龍每個史前怪獸愛好者的腦海里浮現(xiàn)出的是像霸王龍、翼龍這樣的獸腳類掠食者，電腦制作的它們與梁龍、劍龍的打斗也成為俗套。而科學試圖不落窠臼。今年，在拉斯維加斯召開的古脊椎生物學會會議上，一些發(fā)言人問到中生代頂級掠食者是否全是恐龍，結論是否。直到最近還被忽視的一類爬蟲，同樣是重要的食肉動物，正是仍然存活于今的一個族群：鱷魚。

　　That the past role of crocodiles has been underestimated wassuggested a few years ago by Paul Sereno. Dr Sereno, a palaeontologist at the University ofChicago, uncovered a crocodile-dominated ecosystem from about 100m years ago , in what is now north Africa. Besides water-dwelling giants similar to todays animals, he found a range of forms including vegetariansand species that ran on elongated legsmore like dogs than crocodiles. That discovery hasprompted other fossil hunters to look elsewhere. As a result, even the well-studied rocks ofNorth America are revealing that dinosaurs did not have it all their own way in the ecosystemsof the Mesozoicas Stephanie Drumheller of the University of Iowa and Clint Boyd of theUniversity of Texas at Austin explained to the meeting.

　　幾年前，芝加哥大學古生物學家保羅?賽倫諾博士提出鱷魚過去的角色被低估了，在今天的北非，他發(fā)現(xiàn)了一個一億年前由鱷魚占主導地位的生態(tài)系統(tǒng)。除了與現(xiàn)代鱷魚同為水生巨獸外，他還發(fā)現(xiàn)了一系列包括食草的、用長腿行走的比起鱷魚來更像狗的種群及形態(tài)。這一發(fā)現(xiàn)促使其他化石探尋者著眼于其它地方。結果是，即便是那些出自北美的已經(jīng)研究得很透徹的化石也顯示出恐龍并非占據(jù)中生代生態(tài)系統(tǒng)全部位置。正如衣阿華大學的斯蒂芬妮?莊姆海勒以及位于奧斯汀的德克薩斯大學的克林特?博依德在會上說的那樣。

　　The Cretaceous equivalent of zebra and antelopesthe victim species in every wildlifedocumentary about the dramas of the African savannahwere herbivorous dinosaurs calledornithopods. Frequently, these were taken by theropods. But not always. When Ms Drumhellerand Mr Boyd examined the bones of juvenile upper-Cretaceous ornithopods dug up in Utahthey saw marks on one skeleton that looked suspiciously like those modern crocodiles inflictwhen biting and tearing at their prey. On examining these marks more closely, they found acrocodilian tooth stuck in one of them.

　　白堊紀被稱為鳥腳亞目食草恐龍其地位相當于斑馬和羚羊每部有關非洲大草原的紀錄片中被捕殺的種群。這些恐龍經(jīng)常被獸腳亞目食肉恐龍捕食。但不總是這樣，當莊姆海勒與博依德對猶他州出土的白堊紀年幼的鳥腳亞目食草恐龍的化石進行檢查時，他們在一副骨架上發(fā)現(xiàn)了看上去像是遭受現(xiàn)代鱷魚撕咬的痕跡。在對這些痕跡進一步檢查后，他們發(fā)現(xiàn)一顆鱷魚目動物牙齒嵌在其中一塊骨頭上。

　　Crocodile tears

　　鱷魚的眼淚

　　It was not a large tooth. Its size suggests the animal which made it was no more than a metreand a half long. Such a predator would have been unable to take on an adultornithopod. Nevertheless, this tooth is the first unarguable proof that crocodilians did indeedsnack on dinosaurs. Moreover, it helps to confirm suspicions that the other crocodile-bite-likemarks that Ms Drumheller and Mr Boyd have discovered really are what they look like. Bycombining that with an analysis of the whole site, the two researchers argue that what theyhave discovered is a dinosaur nesting ground that was being raided by crocodilians.

　　這顆牙不是很大，其尺寸表明牙齒的主人不超過一米五這樣的掠食者本不能捕食一頭成年鳥腳亞目食草恐龍。但無可爭辯的是，這顆牙是第一個鱷魚目動物拿恐龍當點心的證據(jù)。此外，這也有助于消除對莊姆海勒與博依德發(fā)現(xiàn)的其它看似鱷魚咬痕的懷疑。結合對這個地區(qū)的分析，兩位研究者認為他們所發(fā)現(xiàn)的是一個遭到鱷魚目動物偷襲的恐龍筑巢地。

　　Such suspicions have been aroused before. Other sites in Utah are known to be dinosaurnesting grounds, since eggs are found there. Crocodilian bones frequently turn up at suchsites. Ms Drumheller and Mr Boyd, however, seem to have nailed the connection down. Juveniledinosaurs, at least, were indeed the prey of crocodilians. But what about adults?

　　這樣的懷疑以前也出現(xiàn)過。由于發(fā)現(xiàn)了恐龍蛋，人們知道猶他州還有其它恐龍筑巢地。在這些地區(qū)，鱷魚目動物化石經(jīng)常被發(fā)現(xiàn)。可莊姆海勒與博依德像是要明確這一關系，年幼恐龍至少是鱷魚目動物的獵物，那么成年的呢?

　　More than mere morsels

　　不僅僅是少數(shù)

　　To investigate that question, Martin Lockley at the University of Colorado, Denver, andSpencer Lucas of the New Mexico Museum of Natural History and Science, turned to one of themost famous fossil phenomena on the planetthe dinosaur freeway that runs throughColorado, New Mexico, Kansas and Oklahoma. This collection of tracks, scattered over severalsites of the same age along the coast of an inland sea, is thought to mark an ancientmigration route. The traces of more than 1,380 individual animals can be distinguished.Most, but not all, were ornithopods. Some were small carnivorous dinosaursthe sort thatmight pick off young stragglers in the way that the crocodilians identified by Ms Drumheller andMr Boyd did. But there is, Dr Lockley and Dr Lucas realised, something missing from thepicture. When they looked for traces of big predatory dinosaurs, they found none.

　　為了弄清這一問題，丹佛科羅拉多大學的馬丁?洛克里以及新墨西哥州自然歷史博物館的斯派瑟?盧卡斯將目光轉向世上最著名的化石現(xiàn)象之一橫穿科羅拉多、新墨西哥、堪薩斯、俄荷拉荷瑪?shù)目铸埞贰Ｓ谕荒甏刂粋€內(nèi)陸海海岸分布在數(shù)個地區(qū)，這一匯集恐龍蹤跡的地區(qū)被認為是標出了一條古老的遷徙路線。人們能區(qū)分出超過1380種不同動物的蹤跡。絕大部分是鳥腳亞目食草恐龍。一些是小型食肉恐龍正如莊姆海勒與博依德所確認的鱷魚目動物那樣，這些恐龍會截殺年幼離群的食草恐龍。但洛克里與盧卡斯博士明白，圖上遺漏了一些東西。當他們尋找大型掠食恐龍的線索時，他們什么也沒發(fā)現(xiàn)。

　　That is ecologically absurd. Unless, of course, the top predator of the systemthe one thatcould hunt down adult ornithopodswas not a dinosaur at all. And, when Dr Lockley and DrLucas re-examined the tracks they found that that was exactly what was going on. Instead oftheropod footmarks, they found those of crocodilians. More than a quarter of the places wherethe dinosaur freeway surfaces have yielded signs of crocs. And they were big: sometimes morethan four metres long. That is certainly large enough to take on an adult ornithopod.

　　從生物學上講，這是荒唐的。當然除非生態(tài)系統(tǒng)的頂級掠食者即是能捕殺成年的鳥腳亞目食草恐龍的并不完全是恐龍。而且，當洛克里與盧卡斯博士對這些線索進行重新檢查時，他們發(fā)現(xiàn)那正是曾經(jīng)所發(fā)生的。在出土的恐龍公路上，超過1/4的地區(qū)已發(fā)現(xiàn)鱷魚的蹤跡。而且它們很大：有時超過4米長，大到足以捕殺一頭成年鳥腳亞目食草恐龍。

　　Such megacrocs, then, could easily have acted as top predators in this ecosystem. But thatdoes not completely explain the absence of theropod tracks. Modern migrating herbivores fallvictim to many sorts of carnivore: big cats, wolves and hyenas, to name but three. Themarshy conditions of the dinosaur freeway may, though, have favoured crocodilians over predators that had evolved on drierland. In that sort of environment even a big theropod would constantly have been lookingover its shoulder. Perhaps the real reason why they did not plant their footprints on thedinosaur freeway is that they might have ended up as prey, as well.

　　這樣的巨鱷能在這樣的生態(tài)系統(tǒng)中輕松擔當頂級掠食者的角色。但這并不能完全解釋獸腳亞目食肉恐龍的缺位。現(xiàn)代遷徙類食草動物成為眾多食肉動物的犧牲品：大型貓科動物、狼、鬣狗，就拿這三樣來說。然而，比起在干燥陸地上進化的掠食者，恐龍公路所處的濕地環(huán)境也許更受鱷魚目動物歡迎。在那樣一種環(huán)境下，即便是一頭巨大的獸腳亞目食肉恐龍也會不時回頭張望。它們?yōu)楹螞]有在恐龍公路上留下足跡呢?真正的原因或許是它們同樣亡于其它掠食者。