奇特有喙「地獄雞」是首個以水果為食的恐龍

作者：威爾・丹漢（Will Dunham）By Will Dunham

華盛頓，10月30日（路透社）——恐龍雖然吃過許多不同東西，包括彼此相食，但長久以來，水果似乎一直不在牠們的菜單上。不過科學家如今發現一種火雞大小、沒有牙齒的恐龍化石，牠有著類似鸚鵡的頭部，並展現多項適應特化水果飲食的特徵。WASHINGTON, Oct 30 (Reuters) - While dinosaurs ate a lot of different things, including each other, fruit long seemed to have been absent from their menu. But scientists now have found fossils of a turkey-sized and toothless dinosaur possessing a parrot-like head that exhibited multiple adaptations for a specialized fruit diet.

這種已知首個以水果為食的恐龍名為詹氏地獄雞龍（Infernogallus jamesi），約6600萬年前生活在白堊紀，也就是恐龍時代的暮年。牠的喙與顎部具備可碾碎水果等柔軟食物的特徵。目前已知化石出土於蒙大拿州與北達科他州。This first-known frugivorous dinosaur, named Infernogallus jamesi, lived about 66 million years ago during the Cretaceous Period at the twilight of the age of dinosaurs and displayed traits on its beak and jaws for mashing soft food like fruit. It is known from fossils unearthed in Montana and North Dakota.

Infernogallus這個名稱意為「地獄雞」，一方面是呼應牠類似鳥類的外觀，另一方面則是因為牠的化石發現於地獄溪岩層（Hell Creek rock formation）。該岩層橫跨美國蒙大拿州、北達科他州、南達科他州與懷俄明州，曾產出一些最知名恐龍的遺骸。The name Infernogallus means "hell chicken," a nod to its bird-like appearance and the fact that its fossils were found in the Hell Creek rock formation, which spans the US states of Montana, North Dakota, South Dakota and Wyoming and has yielded the remains of some of the most famous dinosaurs.

牠應是在亞熱帶海岸洪泛平原生態系中吃水果與其他柔軟植物；牠與頂級掠食者暴龍、三角草食恐龍三角龍，以及像坦克般披甲的植食恐龍甲龍等恐龍共享這片環境。It would have eaten fruit and other soft plants in the subtropical coastal floodplain ecosystem it shared with the likes of apex predator Tyrannosaurus, three-horned herbivore Triceratops and tank-like armored plant-eater Ankylosaurus.

地獄雞龍身長約5英尺（1.5公尺），體重約25磅（11.3公斤）。雖然化石——包括一具幾乎完整的骨骼，以及來自顎部與顎骨的零散骨骼——並未顯示羽毛，但研究人員根據其近親化石認為，地獄雞龍身上覆有羽毛。Infernogallus was about 5 feet (1.5 meters) long and weighed around 25 pounds (11.3 kg). While the fossils — one nearly complete skeleton and isolated bones from a jaw and palate — did not reveal feathers, the researchers believe Infernogallus was covered in them, based on fossils of close relatives.

牠屬於獸腳類恐龍，這一類群包括暴龍與所有肉食恐龍，也包括一些轉而吃植物的恐龍，以及整個鳥類譜系。It belonged to a group called theropods that includes T. rex and all the meat-eating dinosaurs, as well as some that took to eating plants and the entire bird lineage.

這項研究的第一作者、紐約州立大學石溪分校古生物學家葛瑞格・芬斯頓（Greg Funston）表示：「這確實擴大了我們原本認為恐龍所具有的生活型態範圍，也顯示獸腳類恐龍有多麼能適應環境。」研究刊登於《自然通訊》（Nature Communications）期刊。"This definitely expands the range of lifestyles we thought dinosaurs had, and it shows how adaptable theropods were," said paleontologist Greg Funston of Stony Brook University in New York, lead author of the research published in the journal Nature Communications.

水果是被子植物的繁殖構造；被子植物也稱為開花植物。被子植物最早出現在白堊紀較早期，約1億3000萬至1億4000萬年前，之後取代了先前由針葉樹、銀杏等裸子植物主導的地景。Fruits are the reproductive structures of angiosperms, also called flowering plants. Angiosperms first appeared earlier in the Cretaceous, around 130 to 140 million years ago, and subsequently took over landscapes previously dominated by plants called gymnosperms like conifers and ginkgoes.

地獄雞龍顯示，一些恐龍可能曾與開花植物有密切的生態關係。Infernogallus shows that some dinosaurs may have had a close ecological relationship with flowering plants.

研究共同作者、加拿大多倫多皇家安大略博物館博士後研究員湯瑪斯・達金（Thomas Dudgeon）表示：「過去曾有人提出，有些恐龍類群吃水果，但一直沒有證據支持。」"It has been proposed before that some groups of dinosaurs ate fruits, but there was never evidence to back it up," said study co-author Thomas Dudgeon, a postdoctoral researcher at the Royal Ontario Museum in Toronto.

達金說：「地獄雞龍的發現顯示，恐龍的飲食很可能遠比我們先前以為的更加多元。在這項發現之前，恐龍演化中有一點謎團。開花植物的演化引入了一種全新的食物來源，毫無疑問對與其共同生活的動物產生了影響。」"The discovery of Infernogallus shows that dinosaur diets were likely far more diverse than we previously thought. Prior to this discovery, there was a bit of a mystery in dinosaur evolution. The evolution of flowering plants introduced a brand-new food source that undoubtedly had consequences for the animals living alongside them," Dudgeon said.

地獄雞龍可取得的水果可能包括各種漿果，以及核果。核果是一個廣泛類別，如今包括桃子、櫻桃等中央有果核的種類，也包括芒果與橄欖等其他種類。The fruit available for Infernogallus may have included various berries as well as drupes, a broad category that today includes types with a central pit like peaches and cherries as well as others like mangoes and olives.

三項關鍵特徵THREE KEY FEATURES

地獄雞龍展現一系列顯示其以水果為食的特徵。芬斯頓表示，其中最重要的三項，是帶動前後咀嚼動作的顎部肌肉配置、使顎部能向前滑動的活動關節，以及喙上一系列有助於碾碎與剪切水果等柔軟植物的脊紋與溝槽。Infernogallus showed a range of features indicating a frugivorous diet. The three most important, Funston said, were the organization of jaw muscles that powered back-and-forth chewing motions, a mobile joint that enabled the jaw to slide forward, and a series of ridges and grooves on the beak to help mash and shear soft plants like fruits.

芬斯頓說：「我們如今在吃柔軟食物的鳥類與龜類身上，會分別看到這些特徵，例如吃無花果的禿鸚鵡，或咀嚼柔軟海草的綠蠵龜。但沒有任何現生動物同時具備這三種適應特徵，這顯示地獄雞龍的特化程度有多高。」"We see these features separately in birds and turtles today that eat soft foods, like the fig-eating vulturine parrot or green sea turtles that chew soft sea grass. But no living animal has all three adaptations, showing just how specialized Infernogallus was," Funston said.

地獄雞龍也顯示，相較於牙齒，喙的適應性更高。Infernogallus also shows how adaptable beaks are compared to teeth.

芬斯頓表示：「一旦失去牙齒、改而發展出喙，只要有某種方式能消化，牠們能取得的食物範圍就會大幅增加，包括植物在內。」"Once you've lost your teeth and developed a beak instead, the range of foods available dramatically increases, including plants, as long as you have some way to digest them," Funston said.

多數草食性獸腳類恐龍使用稱為胃石的石頭來研磨食物。但地獄雞龍與其他竊蛋龍超科近頜龍科（caenagnathids）成員則是以咀嚼方式處理食物。Most herbivorous theropods used stomach stones called gastroliths to grind food. But Infernogallus and other members of a lineage called caenagnathids chewed their food instead.

吃水果的動物會散播種子，對被子植物扮演重要角色。Fruit-eating animals play an important role for angiosperms by dispersing seeds.

芬斯頓說：「哺乳類與鳥類很可能也曾吃水果，但牠們並未展現出地獄雞龍所具備、同樣專門適應水果飲食的特徵，因此水果對牠們來說可能是不那麼重要的資源。白堊紀的哺乳類與鳥類也相當小，因此牠們不太可能傳播非常大的種子，也不太可能把種子傳播到很遠的地方。」"Mammals and birds would probably also have eaten fruit, but they didn't show the same kinds of specializations for a frugivorous diet that Infernogallus does, so it might have been a less important resource for them. Mammals and birds also were quite small in the Cretaceous, so it's unlikely that they were spreading very large seeds, or that they were spreading them big distances," Funston said.

芬斯頓表示：「我們知道，這些大種子的水果當時正在增多並擴散，而近頜龍科似乎可能符合這個角色——不過我們認為，在有把握地建立這項關聯之前，仍需要更多證據。」"We know that these big-seeded fruits were proliferating and spreading, and it seems like caenagnathids could have fit this role — although we feel more evidence is needed before drawing that link confidently," Funston said.

（威爾・丹漢華盛頓報導；丹尼爾・沃利斯編輯）(Reporting by Will Dunham in Washington; Editing by Daniel Wallis)