Determining what extinct dinosaurs ate is difficult, but we can infer some aspects of their dietary preferences.

• dietary 饮食的
• preferences 偏好

Traditionally this information has been derived from direct evidence, such as stomach contents, and indirect evidence, such as establishing a correlation between particular body characteristics and diets of living animals and then inferring habits for dinosaurs.

• correlation 关联
• diet 日常饮食

Animals such as house cats and dogs have large, stabbing canine teeth at the front of the mouth and smaller, equally sharp teeth farther back in their jaws.

• stabbing 尖锐的
• canine 犬的;似犬的;犬
• jaw 颌

Many of these animals are also armed with sharp claws. The advantage of teeth and claws as predatory tools is obvious.

• predatory 捕食的

Now consider animals like cows, horses, rabbits, and mice. These animals have flat teeth at the back of the jaw that are analogous to and have the same function as grindstones.

• flat 扁平的
• analogous 类似的
• grindstone 磨刀石

Unlike the meat-slicing and stabbing teeth of carnivores, the teeth of these animals grind and shred plant material before digestion.

• carnivore 食肉动物
• grind 碾磨
• shred 撕成碎片

More clues exist in other parts of the skull. The jaw joint of carnivores such as dogs and cats has the mechanical advantage of being at the same level as the tooth row, allowing the jaws to close with tremendous speed and forcing the upper teeth to occlude against the lower teeth with great precision.

• joint 关节
• mechanical 机械上的
• occlude 关闭

In herbivorous animals, rapid jaw closure is less important.

• herbivorous 食草的
• closure 关闭

Because the flat teeth of herbivores work like grindstones, however, the jaws mush move both side to side and front to back.

• herbivores 食草动物
• mush 把...碾碎

The jaw joints of many advanced herbivores, such as cows, lie at a different level than the tooth row, allowing transverse tearing, shredding, and compression of plant material.

• transverse 横向的;横切的
• shredding 撕碎;切碎

If we extend such observations to extinct dinosaurs, we can infer dietary preferences (such as carnivory and herbivory), even though we cannot determine the exact diet.

• extinct 灭绝的
• carnivory 肉食性
• herbivory 草食性

The duck-billed dinosaurs known as hadrosaurs are a good example of a group whose jaw joint is below the level of the tooth row, which probably helped them grind up tough, fibrous vegetation.

• hadrosaur 鸭嘴龙
• duck-billed 鸭嘴型的
• fibrous 纤维的
• vegetation 植物

Paleontologists would like to be much more specific about a dinosaur’s diet than simply differentiating carnivore from herbivore.

• paleontologist 古生物学家
• differentiate 区分
• carnivore 食肉动物
• herbivore 食草动物

This finer level of resolution requires direct fossil evidence of dinosaur meals. Stomach contents are only rarely preserved, but when present, allow us to determine exactly what these animals were eating.

• finer 出色的;好的
• resolution 解决
• preserve 保存;保留

In the stomach contents of specimens of Coelophysis (a small, long-necked dinosaur) are bones from juvenile animals of the same species.

• Coelophysis 腔骨龙
• juvenile 幼年的

At one time, these were thought to represent embryonic animals, suggesting that this small dinosaur gave birth to live young rather than laying eggs.

• at one time 曾经
• embryonic 胚胎的

Further research indicated that the small dinosaurs were too large and too well developed to be prehatchling young.

• prehatchling 孵化前的
• young 幼崽

In addition, the juveniles inside the body cavity were of different sizes. All the evidence points to the conclusion that these are the remains of prey items and that, as an adult, Coelophysis was at least in part a cannibal.

• cavity 洞;空穴;腔汇融
• cannibal 食同类的动物;食人者

Fossilized stomach contents are not restricted to carnivorous dinosaurs.

• fossilized stomach contents 石化的胃内容物
• carnivorous 食肉的

In a few rare cases, most of them “mummies” (unusually well preserved specimens), fossilized plant remains have been found inside the body cavity of hadrosaurs.

• mummy 木乃伊
• plant 植物

Some paleontologists have argued that these represent stream accumulations rather than final meals. The best known of these cases is the second Edmontosaurus mummy collected by the Sternbergs.

• Edmontosaurus 埃德蒙顿龙

In the chest cavity of this specimen, which is housed in the Senckenberg Museum in Germany, are the fossil remains of conifer needles, twigs, seeds, and fruits.

• house 容纳
• chest cavity 胸腔
• conifer needles 针叶树的针叶
• twig 细枝

Similar finds in Corythosaurus specimens from Alberta, Canada, have also been reported, indicating that at least two kinds of Late Cretaceous hadrosaurs fed on the sorts of trees that are common in today’s boreal woodlands.

• coprolite 粪化石
• boreal 北方的
• woodland 森林

A second form of direct evidence comes from coprolites (fossilized bodily waste). Several dinosaur fossil localities preserve coprolites. Coprolites yield unequivocal evidence about the dietary habits of dinosaurs.

• unequivocal 不含糊的;明白的;确实的

Many parts of plants and animals are extremely resistant to the digestive systems of animals and pass completely through the body with little or no alteration.

• resistant 抵抗的;反抗的

Study of coprolites has indicated that the diets of some herbivorous dinosaurs were relatively diverse, while other dinosaurs appear to have been specialists, feeding on particular types of plants. The problem with inferring diets from coprolites is the difficulty in accurately associating a particular coprolite with a specific dinosaur.

• diverse 不同的;多种多样的;