Others have blamed extinction on competition from the mammals, which allegedly ate all the dinosaur eggs--except that mammals and dinosaurs appeared at the same time in the Late Triassic, about 190 million years ago, and there is no reason to believe that mammals suddenly acquired a taste for dinosaur eggs after 120 million years of coexistence. (TPO42, 56)
allegedly/?'led?idli/ adv.据称，据传闻
分析：
这个句子的主干就是：
Others have blamed extinction on competition from the mammals
修饰一：(which allegedly ate all the dinosaur eggs)，从句
中文：据说它们吃掉了所有的恐龙蛋
修饰二：(that mammals and dinosaurs appeared at the same time in the Late Triassic, about 190 million years ago,and there is no reason to believe that mammals suddenly acquired a taste for dinosaur eggs after 120 million years of coexistence.) ，从句
注意这个从句里面还有一个从句：
(that mammals suddenly acquired a taste for dinosaur eggs after 120 million years of coexistence)
中文：哺乳动物和恐龙同时出现在约190万年前的晚三叠世，没理由认为哺乳动物在和恐龙共同生活了120万年之后，忽然爱吃恐龙蛋了。
参考翻译：
其他科学家将(恐龙的)灭绝归咎于哺乳动物的竞争，据说它们吃掉了所有的恐龙蛋——只是，哺乳动物和恐龙同时出现在约190万年前的晚三叠世，没理由认为哺乳动物在和恐龙共同生活了120万年之后，忽然爱吃恐龙蛋了。