A new dinosaur species was a plant-eater with yard-long horns over its eye-brows, suggesting an evolutionary middle step between older dinosaurs with evenlarger horns and the small-homed creatures that followed, experts said.
The dinosaur"s horns, thick as a human arm, are like those of tdceratops－whichcame 10 million years later. However, this animal belonged to a subfamily that usuallyhad bony nubbins a few inches long above their eyes.
Michael Ryan, curator of vertebrate paleontology for the Cleveland Museum of Natural History, published the discovery in this month"s Journal of Paleontology. He dugup the fossil six years ago in southern Alberta, Canada, while a graduate student forthe University of Calgary.
"Unquestionably, it"s an important find," said Peter Dodson, a University of Pennsylvania paleontologist."It was sod of the grandfather or great-uncle of the really diverse homed dinosaurs that came after it."
Ryan named the new dinosaur Albertaceratops nesmoi, after the region and Cecil Nesmo, a ranchernear Manyberries, Albeda, who has helped fossil hunters.
The creature was about 20 feet long and lived 78 million years ago.
The oldest known horned dinosaur in North America is called Zuniceratops. It lived 12 million years be-fore Ryan"s find, and also had large horns.
That makes the newly found creature an intermediate between older forms with large hams and latersmall-horned relatives, said State of Utah paleontologist Jim Kirkland, who with Douglas Wolfe identified Zu-niceratops in New Mexico in 1998. He predided then that something like Ryan"s find would turn up. "Lo andbehold, evolutionary theory adually works," he said.
美博物馆确认发现新恐龙
美国俄亥俄州克利夫兰市一博物馆的专家近日表示。他们通过对几年前挖掘出的化石进行研究，已经成功确认了一种此前从未被发现的恐龙。这是一种头上有着多只近1米长的角且以植物为食的恐龙，它其实是恐龙从头上长着很大的角进化到“小角缠头”这一过程内的中间产物。
此种恐龙的角的粗细与人的胳膊相仿，它们看上去非常类似于在其后1000万年才出现的三角恐龙头上的角。这种动物属于那种在其眼睛上方有着长达数英寸的骨质瘤的恐龙的亚科。
迈克尔·瑞安是克利夫兰自然历史博物馆古脊椎动物部门的负责人。他在本月的《古生物学杂志》上对外公布了这一新发现。正是他于6年前在加拿大阿尔伯塔省南部地区亲手发掘出了那些化石，当时他还是该国卡尔加里大学的一名研究生。
美国宾夕法尼亚大学的古生物学家彼得·多德森表示：“毫无疑问。这是一个十分重要的发现。它从某种程度上可以说是后来那些多种多样的头上长角恐龙的远祖。”
由于本次挖掘工作得到了居住在阿尔伯塔省迈尼贝里市附近的—位名叫塞西尔·内斯莫的农场工人的帮助。所以瑞安特地将这种新发现的恐龙命名为阿尔伯塔角龙内斯莫伊。
该恐龙的体长约为20英尺(6.1米)左右，其生活年代则在距今7800万年前。
目前在北美地区发现的最为古老的有角恐龙是祖尼角龙。它生活的年代比上面所说的那个恐龙还要早上1200万年，其头上同样长着多只硕大的角。
美国犹他州立大学古生物学家吉姆·柯克兰德表示，本次发现填补了在较为古老的大角恐龙与晚近出现的小角恐龙之间存在的空缺，也正是他在1998年时与道格拉斯·伍尔夫一起于新墨西哥州发掘并最终确认了祖尼角龙。他当时还曾预测人们在未来将会找到类似于瑞安本次所发现的这种恐龙。